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The thyroid is
a small, butterfly-shaped gland located in the front of the neck
that produces hormones that increase oxygen use in cells and stimulate
vital processes in every part of the body. These thyroid hormones
have a major impact on growth, use of energy, heat production, and
infertility. They affect the use of vitamins, proteins, carbohydrates,
fats, electrolytes, and water, and they regulate the immune response
in the intestine. They can also alter the actions of other hormones
and use of thyroid hormones is a complex and important process:
in this intricate system of glands and hormone synthesis and production
can have far-reaching consequences.
- An understanding
of the complex thyroid hormone process begins with iodide,
a salt that is extracted from the blood and trapped by the thyroid
is converted to iodine in the thyroid gland. (Here, 80%
of the body's iodine supply is then stored.) Iodine, in turn,
is the raw material used in the manufacturing of thyroxine
(T4), the key thyroid hormone.
itself is converted into triiodothyronine (T3) , which
is the more biologically active thyroid hormone. (Only about
20% of triiodothyronine is actually formed in the thyroid gland,
however. The rest is manufactured from circulating thyroxine
in tissues outside the thyroid, such as those in the liver and
- Once the
T4 and T3 thyroid hormones are in circulation, a large fraction
binds to other substances called thyroid hormone transport proteins,
after which they become inactive. (In fact, only 0.03% of thyroxine
and 0.5% of triiodothyronine are free, that is, unbound, and
- Two other
important hormones in the process are thyroid-stimulating
hormone ( TSH or thyrotropin) and thyrotropin-releasing
hormone ( TRH).
- TSH directly
influences the whole process of iodine trapping and thyroid
- This hormone
is secreted by the pituitary gland and monitored by TRH, which
is produced in the hypothalamus gland. (Both the pituitary and
hypothalamus glands are located in the brain.)
- When thyroxine
levels drop even slightly, the pituitary gland goes into action
to pump up secretion of TSH so that it can stimulate thyroxine
occurs when secretion of thyroid hormones is inadequate to the point
that the body begins to slow down. Hypothyroidism was first diagnosed
in the late nineteenth century when physicians observed that after
surgically removing the thyroid gland, a patient developed swelling
of the hands, face, feet, and tissues around the eye. They named
this syndrome myxedema and correctly concluded that it was
the outcome of the absence of substances, thyroid hormones, normally
produced by the thyroid gland. Hypothyroidism is usually progressive
and irreversible. Treatment, however, is nearly always completely
successful and allows a patient to live a fully normal life.
or temporary conditions can reduce thyroid hormone secretion and
cause hypothyroidism. The most common of these are Hashimoto's thyroiditis,
an autoimmune condition, and overtreatment of hyperthyroidism.
About 95% of hypothyroidism cases occur from problems that originate
in the thyroid gland. In such cases, the disorder is called primary
hypothyroidism. In some cases, it is caused by disorders of the
pituitary gland (when it is known as secondary hypothyroidism) or
hypothalamus gland (tertiary hypothyroidism).
is a primary hypothyroid disease. In any autoimmune disease, the
body's immune system attacks its own cells. In the case of autoimmune
thyroiditis, the cells under attack are in the thyroid gland. Experts
do not know why the immune system starts to injure the thyroid.
There are a number of theories to account for it.
The most common
autoimmune diseases of the thyroid are Hashimoto's thyroiditis,
atrophic thyroiditis, and postpartum thyroiditis.
- One theory
is that a virus or bacteria with a protein resembling a thyroid
protein might trigger the response. This theory is backed up
to some extent by the presence of recent infections in people
with autoimmune disease. There is an association between hepatitis
C, for instance, and the onset of autoimmune hypothyroidism.
- Some experts
believe the infectious-disease theory is not convincing. An
alternative hypothesis is that certain patients have abnormal
thyroid cells, possibly from a genetic defect, that provoke
a suicidal process called apoptosis that leads to a direct
attack by T-cells, important agents in the immune-system.
Hashimoto's Thyroiditis. The most common form of hypothyroidism
in the US is Hashimoto's thyroiditis, a genetic disease named after
the Japanese physician who first described thyroid inflammation
in 1912. It occurs in approximately 0.3 to 5 people per 1000 per
year, and women are 15 to 20 times more likely than men to develop
this disease. An enlargement of the thyroid gland called a goiter
is almost always present, which may appear as a cyst-like or fibrous
growth in the neck. Hashimoto's thyroiditis is permanent and requires
life-long treatment. Both genetic and environmental factors appear
to play a role in its development.
One interesting theory holds that Hashimoto's thyroidism and Graves'
disease (which is caused by hyperthyroidism) are caused by
a similar immunologic dysfunction. The antibodies present in both
diseases are similar, and some experts believe that the predominance
of one or another antibody determines which of the diseases become
manifest. The two diseases then, are essentially two sides of a
Atrophic Thyroiditis. Atrophic thyroiditis is similar to
Hashimoto's thyroiditis, except a goiter is not present.
Riedel's Thyroiditis. In a rare autoimmune disorder known
as Riedel's thyroiditis, patients develop a hard stony mass that
suggests cancer, but the disorder responds well to thyroid replacement
Women are at
much higher risk for hypothyroidism during or after pregnancy, which
affects the thyroid in a number of ways. Iodine requirements increase
because of the needs of both the mother and the fetus. Reproductive
hormones cause changes in thyroid hormone levels. Often, however,
hypothyroidism occurs because women develop antibodies to their
own thyroid during pregnancy, causing an inflammation of the thyroid
after delivery. Autoimmune thyroiditis occurs in up to 5% of pregnant
women and tends to develop between four and 12 months after delivery
(and so is called postpartum autoimmune thyroiditis). It almost
always resolves on its own. However, in one study of women who had
postpartum thyroiditis, hypothyroidism developed three to five years
after the pregnancy in 23% of cases. Occasionally, postpartum hypothyroidism
can also be permanent after pregnancy, particularly in women who
have had recurrent episodes after previous pregnancies and in women
who have other autoimmune disorders. Postpartum thyroiditis may
be interrupted by bouts of hyperthyroidism as well.
Too much or too
little iodide can cause hypothyroidism. If there is a deficiency
of iodide, then the body cannot manufacture thyroxine. Too much
iodide is a signal to inhibit the conversion process of thyroxine
to T3. The end result in both cases is inadequate production of
Iodine Deficiencies. Diets deficient in iodine can lead
to hypothyroidism. About 200 million people around the world have
hypothyroidism because of insufficient iodine in their diets. The
presence of iron-deficiency anemia, another problem prevalent among
iodine-deficient children in developing countries, further exacerbates
hypothyroidism in these children and impedes the efficacy of iodine
supplementation. (Iron supplements may help such patients. It is
extremely important to note, however, that iron supplements can
be very dangerous in children, even at normal adult levels. No one
should give children iron without a physician's recommendation.)
Up to half of
patients who receive radioactive iodide develop permanent hypothyroidism
within a year of therapy. This is the standard treatment for Graves'
disease, which is the most common form of hyperthyroidism,
a condition caused by excessive secretion of thyroid hormones.
By the end of five years, about 65% of treated patients have developed
hypothyroidism, after the rate of this condition levels off to about
1% a year. Such patients need to take thyroid hormones for the rest
of their lives. Other forms of treatment for overactive thyroid
glands using either antithyroid drugs or surgery may also result
in hypothyroidism. [ See Thyroid Surgery, below.]
(total thyroidectomy) of the thyroid to treat thyroid cancer requires
a lifetime of treatment with an appropriate dosage of thyroid hormone.
Removing one of the two lobes of the thyroid gland (hemithyroidectomy),
because of benign growths on the thyroid gland, rarely produces
hypothyroidism. The remaining thyroid lobe will generally enlarge
so that it can produce sufficient amounts of thyroid hormone for
normal function. Many physicians recommend thyroid hormone treatment,
however, to prevent the formation of additional nodules. The small
percentage of Graves' disease patients who require surgery to remove
most of both thyroid lobes (subtotal thyroidectomy) may develop
hypothyroidism. It is important to find an experienced surgeon for
this procedure and to have the thyroid checked at six- or 12-month
of Hypothyroidism in Infants
Congenital Hypothyroidism. Hypothyroidism in newborns (known
as congenital hypothyroidism) occurs in about .04% of infants,
and in 90% of these cases it is life long. The development of the
thyroid, pituitary, and hypothalamus and the mechanisms that affect
hormone production is a complex one and any one of many abnormalities
during pregnancy can cause hypothyroidism. In up to 85% of congenital
hypothyroidism cases, the thyroid gland is either missing, underdeveloped,
or not properly located. There does not appear to be any inherited
factor or recognizable cause in the great majority of these cases.
In about 10% to 15% of cases, there are abnormalities in the processes
involved in hormone production. Most of these cases are likely to
be due to inherited factors. In less than 5% of cases, the pituitary
or hypothalamus glands function abnormally. The causes of this situation
vary and can include inherited or brain abnormalities.
Temporary Hypothyroidism in Infants. Temporary hypothyroidism
can also occur in premature infants from various factors:
thyroid disease and thyroid dysfunction in the mother may be
responsible for about half of the cases of temporary hypothyroidism
hypothyroidism in infants can also occur in mothers who are
being treated for thyroid disease.
- The central
nervous system connections between the hypothalamus and pituitary
glands may also mature late; this condition generally resolves
between four to 16 weeks after birth.
that Reduce Thyroid Levels
Lithium, a drug widely used to treat psychiatric disorders, has
multiple effects on thyroid hormone synthesis and secretion. Up
to 50% of patients who take lithium develop goiter, with 20% developing
symptomatic hypothyroidism, and another 20% to 30% developing hypothyroidism
Amiodarone. The drug amiodarone (Cordarone), which is used
to treat abnormal heart rhythms, contains high levels of iodine
and can induce hyper- or hypothyroidism, particularly in patients
with existing thyroid problems. Hypothyroidism is the more common
effect in the US, where dietary iodine is abundant, although hyperthyroidism
is not an unknown effect. In patients with normal thyroids, amiodarone
causes triiodothyronine levels to fall by 20 to 25%, and between
5 and 25% of patients develop hypothyroidism.
Antiseizure Agents. Drugs used for epilepsy, including phenytoin
and carbamazepine, reduce thyroid levels.
Other Drugs. Certain antidepressants may cause hypothyroidism,
although this effect is infrequent. Many other drugs contain iodine
or have properties that affect the thyroid, although their effects
are almost always reversible when they are stopped. Large doses
of selenium, a common over-the-counter supplement, may lower thyroid
levels. Some drugs used in chemotherapy can cause hypothyroidism.
for cancers of the head or neck and for Hodgkin's disease can cause
hypothyroidism in up to 65% of patients within 10 years after treatment.
Exposure to radiation from nuclear power plants may be associated
with thyroid disorders, but further research is needed. A study
of children living near Chernobyl during the nuclear accident in
1986 found that nearly 20% of them who were heavily exposed to radiation
had indications of thyroid autoantibodies. Females who at the time
were older than 13 years old had the highest risk. At the time of
the study, in 1992 and 1994, none of the children had developed
hypothyroidism, but experts recommended monitoring them. In another
study of people exposed to radioactive iodine from the Hanford Nuclear
Site between 1955 to 1957, individuals exposed to high doses were
no more likely to develop thyroid disease than those who were exposed
to low doses. The study did not address whether radiation exposure
caused an increase of thyroid disease in general, however.
and Tertiary Hypothyroidism
In rare instances,
usually due to a tumor, the pituitary gland will fail to produce
thyrotropin (TSH), the hormone that stimulates the thyroid to produce
its hormones. In such cases, the thyroid gland withers. When this
happens, secondary hypothyroidism occurs.
ARE THE SYMPTOMS OF HYPOTHYROIDISM?
has a broad range of effects. Physicians report, however, that most
patients with thyroid abnormalities are identified in early stages
when symptoms are mild, a condition called subclinical hypothyroidism
. In such patients, blood tests indicate slightly elevated TSH
levels. There may be no symptoms at all other than mild fatigue.
This condition progresses to overt hypothyroidism in about 2% of
all untreated people per year. In older women, however, the rate
is much faster, about 17% per year. The symptoms increase as the
disease progresses and the metabolism slows down.
As free thyroxine levels fall over the following months, other
- Many people
attribute the early symptoms of hypothyroidism to stress or
aging, including feeling chronically tired and overly sensitive
- In one
study, 30% of people with hypothyroidism developed headaches
within one to two months of the onset of the thyroid disorder.
Those with a history of migraines were at higher risk for this
symptom. The headaches were mild but continuous and on both
sides of the head.
and joint aches often develop.
gain is common even though appetite diminishes.
can be a problem.
women may experience heavy periods or, in rare cases, a milky
discharge from the breasts.
- A history
of miscarriage may be a sign of impending hypothyroidism. Studies
suggest that even if thyroid levels are normal, women who have
a history of miscarriages often have antithyroid antibodies
during early pregnancy and are at risk for developing autoimmune
thyroiditis over time.
activity, including concentration and memory, may become slightly
impaired, particularly in the elderly.
develops. Some experts believe that even mild thyroid failure
may increase susceptibility to major depression.
affects muscles. Weakness and pain may occur. Muscle cramps
are common. In some cases it causes carpal tunnel syndrome or
symptoms similar to gout or arthritis. In some cases the arms
and legs may feel numb.
- Some people
experience hearing loss.
- The voice
may become husky.
sleep apnea is common, in which tissues in the upper throat
collapse at intervals during sleep, thereby blocking the passage
- If untreated,
the classic physical changes characteristic of myxedema can
develop: a round puffy face with a sleepy appearance, dry, rough
skin, and loss of hair.
of Secondary Hypothyroidism (Caused by Pituitary Growth)
caused by pituitary growth, produces the usual symptoms of primary
hypothyroidism, and, in addition, sexual drive and fertility may
be impaired in both men and women. Patients may also be exhausted,
crave salt, and have low blood pressure. Headaches and visual disturbances
may develop, which are directly related to the pituitary tumor.
in Infants and Children
All babies are
now screened for hypothyroidism in order to prevent retardation
that can occur if the disorder is not detected early. Symptoms of
hypothyroidism in children vary depending on when it first develops.
- Most children
who are born with a defect that causes congenital hypothyroidism
have no obvious symptoms. When symptoms do exist in the newborn
they may include the following: jaundice (yellowish skin), noisy
breathing, and enlarged tongue.
- If hypothyroidism
is not detected and treated, early symptoms in the infant include
the following: feeding problems, failure to thrive, constipation,
hoarseness, and sleepiness.
on, symptoms in untreated children include protruding abdomens,
rough, dry skin, and delayed teething.
- If they
do not receive proper treatment in time, children with hypothyroidism
may be extremely short for their age, have a puffy, bloated
appearance, and have below-normal intelligence. Any child whose
growth is abnormally slow should be examined for hypothyroidism.
IS HYPOTHYROIDISM DIAGNOSED?
Advances in diagnostic
methods now make it possible to detect hypothyroidism in almost
all cases before severe symptoms develop. Physicians can make the
diagnosis of hypothyroidism after completing a history and physical
exam of the patient and performing sensitive laboratory tests on
the patient's blood. [ See Box , Screening Recommendations
Thyroid Hormone Levels
of TSH. Blood tests that measure thyroid-stimulating hormone
(TSH or thyrotropin) levels are the most sensitive indicators of
When thyroxine (T4) levels drop even slightly, the pituitary gland
goes into action to pump up secretion of TSH so that it can stimulate
thyroxine production. In fact, thyroxine may still be within normal
range when the pituitary begins to increase the supply of TSH.
that TSH levels should not be the sole criterion for diagnosing
hypothyroidism, but should be interpreted in the context of the
patients' symptoms, the effects of drug therapies, the serum thyroxine
levels, and the presence of autoantibodies.
levels are generally between 0.5 to 5.0 mU/L. If TSH levels
are elevated above 6 mU/L, regardless of thyroxine levels, the
physician can still make a diagnosis of hypothyroidism.
- In nearly
all cases, thyroid replacement treatments should begin when
levels are above 10mU/L.
- It is
not clear, however, at what point subclinical hypothyroidism
(generally between 5 mU/l and 10 mU/L) should be treated. (The
condition is referred to as subclinical if TSH is elevated but
thyroxine levels are normal and the patient has no obvious symptoms.)
Measurement of other Thyroid Hormones. Thyroxine itself is sometimes
measured. For instance, in the very elderly, seriously ill patients,
and during pregnancy, both thyroxine and TSH levels may be extremely
variable. Therefore, the physician should repeat measurements of
both hormones before starting thyroid-hormone therapy in such patients.
Additional tests may improve accuracy, including tests known as
free thyroxine (fT4), T3 resin uptake, and sensitive thyroid-stimulating
hormone (sTSH) assays.
will check the heart, eyes, hair, skin, and reflexes for signs of
Goiter. The presence of a goiter (an enlarged thyroid), especially
a rubbery, painless one, may be an indication of Hashimoto's disease.
If the thyroid is tender and enlarged but not necessarily symmetrical,
the physician may suspect subacute thyroiditis. A diffusely enlarged
gland may occur in hereditary hypothyroidism, in postpartum patients,
or from use of iodides or lithium. Goiters may also develop in people
with iodide deficiency.
Thyroid Neck Check. Women who are experiencing menopausal
symptoms which may be masking those of hypothyroidism should perform
a simple self-examination called the Thyroid Neck Check. [See Box
Thyroid Neck Check.]
Hold a mirror in front of the area of the neck where the thyroid
gland is located.
This area is just below the Adam's apple and right above the
collarbone. (Note: The Adam's apple is not the thyroid location.)
Tip the head back.
Take a drink of water and swallow, watching the neck during
Check for any bulging or protrusions. If any is detected,
call a physician for a check up.
A blood test
for certain antithyroid antibodies is sometimes used to detect Hashimoto's
thyroiditis, particularly in patients who have knobby goiters. Such
tests identify antibodies against a factor called thyroperoxidase.
If high levels of antibodies are present, Hashimoto's thyroiditis
is a certain diagnosis. Even if patients have no symptoms at the
time of the test, a positive result usually means that a patient
has a 4% to 8% chance of developing symptoms each year.
Thyroid scintigraphy tests scan the thyroid and pick up images highlighted
by small amounts of radioactive substances. Thyroid scans can be
used to determine whether the thyroid is producing normal amounts
of hormone. The patient drinks a small amount of radioactive iodine
or technetium and waits until it has been through the thyroid. Images
of a properly functioning thyroid would show uniform levels of absorption
throughout the gland. Overactive areas would show up white and underactive
areas would appear dark. Thyroid scans are usually unnecessary unless
the physician needs to rule out suspected cancer.
Ultrasound. Ultrasound has limited value, but it can visualize
the thyroid and specific abnormalities, such as nodules. (It cannot
measure the thyroid gland's function, however.)
More Advanced Imaging Tests. If laboratory tests suggest
that a pituitary or hypothalamus problem is causing hypothyroidism,
the physician will usually order brain imaging procedures using
computed tomography (CT) scans or magnetic resonance imaging (MRI).
MRIs may also be used for determining the extent of thyroid cancers
and of goiters. MRIs are also being used for investigating hypothyroidism
in infants and for determining widespread effects of autoimmune
thyroiditis (such as Hashimoto's hypothyroidism).
biopsy is a common procedure performed in a doctor's office and
used to obtain thyroid cells for microscopic evaluation. Much like
drawing blood, the physician injects a small needle into the thyroid
gland and draws cells from the gland into a syringe. The cells are
put onto a slide, stained, and examined under a microscope. It may
be used for patients with suspected Hashimoto's hypothyroidism,
especially if they have difficulty swallowing or develop a goiter.
need to be checked. Other blood tests may be performed to detect
levels of calcitonin, calcium, prolactin, and thyroglobulin and
to check for anemia and liver function, all of which may be affected
SCREENING RECOMMENDATIONS FOR HYPOTHYROIDISM
Screening in Older Adults
believe that because thyroid problems are so common in the
elderly and thyroid hormone tests are so inexpensive, blood
tests for thyroid function should be routine. Undiagnosed
hypothyroidism in elderly patients can develop into a serious
and even life-threatening situation. Hyperthyroidism also
poses many health risks. In fact, during the period around
menopause, the symptoms of menopause and hypothyroidism are
similar and can easily be confused with each other.
Professional organizations differ widely on screening recommendations.
Most do not recommend widespread screening for healthy adults:
The American College of Physicians recommends that women
over 50 years old should be screened for thyroid disorders
every five years. And, the American Academy of Family
Physicians believes that adults do not have to be screened
until they are over 60 years old.
The American Thyroid Association, however, recommends
that all adults, both men and women, begin their screening
at age 35 and every five years afterward. Experts in this
organization argue that such early screening is inexpensive
and would prevent progression to hypothyroidism, and therefore
possibly heart disease, in people with subclinical hypothyroidism.
Such an approach would also eliminate the need for expensive
Screening During Pregnancy
untreated hypothyroidism is a serious problem for the unborn
child, all pregnant women should be tested for thyroid function.
It should be noted that elevated levels of estrogen during
pregnancy cause thyroid hormone levels to rise, so even if
a pregnant woman has an underactive thyroid, test results
for thyroxine may actually be normal. A blood test showing
elevated TSH levels, however, would be a reliable indicator
of an underactive thyroid, even during pregnancy.
Screening in Infants
It is very
difficult to diagnose hypothyroidism in newborns by symptoms
alone. Fortunately, almost all newborns with hypothyroidism
are identified shortly after birth through an effective national
screening program using a thyroid blood test. Each year over
1,500 children are now saved from subnormal intelligence.
Out Other Disorders
of hypothyroidism are so similar to common conditions, including
just aging, it often makes diagnosis difficult.
Conditions that Cause Thyroid Abnormalities. Some conditions
may cause thyroid abnormalities without symptoms and must be differentiated
from subclinical hypothyroidism. They include, although are not
limited to, the following:
Disorders. Some symptoms of hypothyroidism and aging are very
similar. Menopausal symptoms often resemble hypothyroidism. Many
other problems related to aging, such as vitamin deficiencies, Parkinson's
and Alzheimer's diseases, and arthritis also have characteristics
that can mimic hypothyroidism.
response to thyroid therapies in people with hypothyroidism.
from a severe illness that is unrelated to thyroid disorders.
of the adrenal gland.
Obesity. Many people who are overweight believe that they
have an underactive thyroid gland, but only a very small percentage
of obese people actually have hypothyroidism. Hypothyroid patients
generally show only a moderate weight increase of five to 10 pounds,
mainly from accumulation of fluid, and in fact they often have a
Depression. A lack of interest in personal relationships,
drowsiness, an increase in sleep, slowing of speech, and general
apathy are signs of clinical depression as well as hypothyroidism.
The two disorders, in fact, often coexist, particularly in older
women, so diagnosing one does not rule out the presence of the other.
Diseases of Muscles and Joints. Joint and muscle pain may
be the first symptoms of hypothyroidism. Most likely, however, such
pain is not caused by hypothyroidism if other thyroid symptoms remain
absent. Numerous conditions can cause muscle and joint pain, and
if thyroid levels are normal the physician should look for other
As many as 13
million Americans have a thyroid disorder. Studies suggest that
between 1% and 10% of the global population has some evidence of
abnormally low thyroid hormones. (As previously mentioned, subclinical
hypothyroidism is a condition with thyroid abnormalities but no
or mild symptoms.)
failure occurs eventually in 4% to 21% of women and 3% to 16% of
men, with the risk increasing with age.
Women. In all age groups, women have a higher risk than men,
although the difference is significant only after age 34. In one
study, nearly 6% of women over 60 had hypothyroidism, and some experts
estimate that as many as 20% of women in this age group have a subclinical
condition (low blood levels of thyorid but no or mild symptoms).
In fact, the symptoms of hypothyroidism and menopause are very similar
and hypothyroidism may easily be missed. Pregnant women have a 2.5%
to 5% incidence of postpartum thyroiditis, which develops into hypothyroidism
in about 23% of cases three to five years later.
Men. In one survey, nearly as many men over age 74 had subclinical
hypothyroidism (16%) as women their age (21%).
The elderly are
most susceptible, but hypothyroidism can affect people of all ages.
For example, one out of every 4,000 infants is born with congenital
hypothyroidism; female infants are at higher risk than males.
a role in both underactive and overactive thyroid. About half of
those with close relatives with chronic autoimmune disease have
antibodies to the thyroid. (Antibodies are the immune system's agents
for attacking specific foreign substances, such as microbes.) Thyroid
disease will often skip generations; someone with an underactive
thyroid may have healthy parents but have grandparents who had thyroid
troubles. Some people inherit a tendency to thyroid problems but
never become ill, while others become very sick. As many as half
of those with Turner's syndrome, one of the most common genetic
diseases in women, have hypothyroidism, usually in the form of Hashimoto's
1 Diabetes and Other Autoimmune Diseases
About 10% of
patients with type 1 (insulin-dependent) diabetes develop chronic
thyroiditis, which in turn can lead to subclinical hypothyroidism.
This condition may affect insulin requirements, so such patients
should have regular examinations for hypothyroidism. Women with
other autoimmune diseases, including systemic lupus erythematosus,
pernicious anemia, and rheumatoid arthritis, are also at higher
risk for hypothyroidism. Pregnant women with autoimmune conditions
have a 25% risk for hypothyroidism during gestation.
the risk for developing thyroid disease, particularly autoimmune
hyper- and hypothyroidism. According to a 1998 study, smoking also
increases the negative effects of hypothyroidism in patients who
already have the condition. Pregnant women with subclinical hypothyroidism
who smoke between one and two packs of cigarettes daily are at risk
for even lower thyroid function than their nonsmoking peers. These
women may also develop significantly higher levels of total cholesterol
and LDL, the so-called bad cholesterol, than non-smoking women with
exists between breast cancer and increased levels of thyroid autoantibodies,
indicating that many women with breast cancer may be susceptible
to hypothyroidism. (The presence of these autoantibodies, however,
is a favorable indicator for survival in women who develop breast
occasionally occurs with Addison's disease and myasthenia gravis.
It is also associated with ovarian failure, sleep apnea, premature
gray hair, and left-handedness. People with anorexia or bulimia
are at risk for hypothyroidism; in these cases, however, reduced
thyroid function may be an adaptation to malnutrition and therefore
some experts think only that the eating disorder should be treated,
not hypothyroidism. Because so many drugs affect the thyroid, anyone
being treated for a chronic disease, patients who are taking thyroid
medication, and those who are at risk for thyroid disorder should
discuss the impact these drugs may have on their thyroid.
SERIOUS IS HYPOTHYROIDISM?
carries serious physical and mental risks for all ages. Studies
indicate that subtle adverse health effects occur even with subclinical
hypothyroidism, a condition in which the patient has no symptoms
but blood tests indicate hypothyroidism. Fortunately, hypothyroidism
is now easily diagnosed, and treatment will restore normal thyroid
function and relieve symptoms and physical signs of the disease.
With treatment, a patient should expect to live a normal life, free
of harmful consequences. It should be noted, however, that iodine
deficiency and goiter are still major problems in less developed
nations, causing varying degrees of mental retardation in millions
on the Heart
notably triiodothyronine (T3), affect the heart directly and indirectly.
They are closely linked with heart rate and heart output. T3 provides
particular benefits by relaxing the smooth muscles of blood vessels
thus helping to keep them open so blood may flow smoothly through
them. Hypothyroidism is associated with unhealthy cholesterol levels,
mild high blood pressure, impaired heart muscle contraction, and
heart failure in people with existing heart disease. There is some
evidence that even subclinical hypothyroidism increases the
rates of heart disease and heart attacks in older women.
Cholesterol and Lipid Levels. According to one 2000 study,
hypothyroidism is only second to poor dietary habits as a cause
of high cholesterol. Studies have reported a higher risk for high
levels of low-density lipoprotein (LDL) cholesterol (the "bad" cholesterol)
and a cholesterol-carrying molecule called lipoprotein(a), both
of which are major risk factors in heart disease. Treatment can
significantly reduce total cholesterol, LDL, and lp(a), helping
to prevent the development of coronary artery disease. Some studies
report that total and LDL cholesterol levels are higher than normal
even in people with subclinical hypothyroidism (TSH levels between
5.1 and 10 mU/L). Research on whether the association between mild
hypothyroidism and cholesterol levels is significant are mixed,
Effects on Blood Flow. One 2000 study suggests that impaired
blood flow, which occurs with subclinical hypothyroidism, may play
a significant role in heart disease and a heart attacks in older
women. Some experts believe that studies showing less of an effect
may have underestimated the situation because of their emphasis
on cholesterol levels. Homocysteine. Recent studies are also
finding that hypothyroidism is associated with elevated levels of
homocysteine, an amino acid that is increasingly becoming a major
suspect in heart diseases.
Blood Pressure. Hypothyroidism may slow the heart rate to
less than 60 beats per minute and reduce the heart's pumping capacity.
For this reason there has been some concern about an increased risk
for high blood pressure. One study found no such association, at
least in older women. Studies published in 1999 and 2001, however,
reported changes in blood vessel properties that affect blood pressure
even in patients with subclinical hypothyroidism. In any case, hypothyroidism
does increase the risk for high blood pressure in pregnant women,
and all patients with chronic hypothyroidism should have their blood
pressures checked regularly.
is also commonly associated with iron deficiency anemia and respiratory
problems. Some research has associated hypothyroidism with an increased
risk for glaucoma. Hypothyroidism may also worsen headaches in people
predisposed to them.
is not treated, or if drugs, infections, stress, or other traumatic
situations worsen existing hypothyroidism, an emergency condition
can develop with severe manifestations of myxedema, including a
severe drop in body temperature (hypothermia), seizures, stupor,
and finally coma.
on the Mind
Depression is common in hypothyroidism and can be severe. Some psychiatrists
suspect that even subclinical hypothyroidism may contribute to depression.
The two disorders may have some common physiological basis. In one
study, both triiodothyronine (T3) and L-tryptophan (a chemical important
in depression) appeared to be taken up by red blood cells using
the same carrier. Interesting implications of the study are that
alterations in one substance may affect the other. Adding thyroid
hormones to antidepressants, in fact, hastens a depressed patient's
recovery, even in some patients who have not been diagnosed with
hypothyroidism. Hypothyroidism should be considered as a possible
cause of any chronic depression, particularly in older women.
Mental and Behavioral Impairment. Untreated hypothyroidism
can, over time, cause mental and behavioral impairment and eventually,
even dementia. Whether treatment can completely reverse problems
in memory and concentration is uncertain, although many experts
believe that only mental impairment in hypothyroidism that occurs
at birth is permanent.
on Infertility and Pregnancy
Most women with
hypothyroidism fail to produce eggs, and, in fact, many younger
women with hypothyroidism are diagnosed with the condition for the
first time during a fertility evaluation. A pregnant woman with
hypothyroidism has a fourfold risk for miscarriage. In one study,
nearly 40% of women with a history of miscarriages and normal thyroid
levels had antithyroid antibodies (immune factors that attack thyroid
tissue). Those who remain hypothyroid near the time of delivery
are in danger of developing high blood pressure and premature delivery.
They are also prone to postpartum thyroiditis, which is said to
be a contributor to postpartum depression.
on Infants and Children
Untreated Mothers. Children born to untreated pregnant women
with hypothyroidism are at risk for impaired mental performance,
including attention problems and verbal impairment. Studies on children
of women with subclinical hypothyroidism are less clear. In one
study, children between the ages of seven and nine whose mothers
of had subclinical hypothyroidism during pregnancy had IQs that
were seven points lower than children with mothers without the disorder
during pregnancy. Others have reported no significant differences.
Effects of Hypothyroidism in Infancy. Infants born with
congenital hypothyroidism need to receive treatment as soon as possible
after birth to prevent mental retardation, stunted growth, and other
aspects of abnormal development (a syndrome referred to as cretinism).
It has been estimated that untreated infants can lose up to three
to five IQ points per month during the first year. An early start
of life-long treatment avoids or minimizes this damage. According
to a 1999 Canadian study, however, children with congenital hypothyroidism
who had been given early treatment still had a higher risk of learning
disabilities in the third grade. By the sixth grade they had caught
up in some areas, but problems in memory, attention, and spatial
processing persisted into adolescence.
Transient hypothyroidism is common among premature infants. Although
temporary, severe cases can cause difficulties in neurologic and
Effects of Hypothyroidism that Develops in Older Children.
If hypothyroidism develops in children after two years, mental retardation
is not a danger, but physical growth may be slowed and new teeth
delayed. If treatment is given late, adult growth could be affected.
Even with treatment, some children with severe hypothyroidism may
have attention problems and hyperactivity.
Effects of Childhood X-Ray Treatments
Two million Americans,
mostly children, received x-ray treatments to the head or neck between
1920 and 1960 for acne, enlarged thymus gland, recurrent tonsillitis,
or chronic ear infections. The risk of developing thyroid nodules
and thyroid cancers is increased in these individuals. Cancer can
develop as long as 40 years after the original treatment; it is
a particular risk in those treated who develop hypothyroidism. Everyone
who has had head and neck radiation should be sure to have their
thyroid glands examined regularly.
IS HYPOTHYROIDISM TREATED?
In the nineteenth
century, a few years after a relationship was observed between myxedema
and surgical removal of the thyroid gland, physicians began to feed
hypothyroid patients whole or powdered extracts of animal thyroid
glands. This was one of the first successful medical treatments
based on careful scientific observation. Although synthetic thyroid
is now used most often, the therapeutic principle for hypothyroidism
is the same as it was 100 years ago: to provide the body with replacement
thyroid hormone when the gland is not able to produce enough itself.
It is clear that
the following condition warrants treatment with thyroid replacements:
however, can now diagnose subclinical hypothyroidism (when TSH levels
are slightly higher than normal but thyroxine levels are normal
and there are no obvious symptoms). There are a number of arguments
for treating subclinical hypothyroidism, but evidence on all of
its benefits is still uncertain:
hypothyroidism with clear symptoms and blood tests that show
high TSH (generally 10 mU/L and above) and low thyroxine must
In addition to
the lack of clear evidence on the cost-effective benefits of treating
subclinical hypothyroidism, experts argue that thyroid levels can
vary widely and subclinical hypothyroidism may not persist. In such
cases, overtreatment leading to hyperthyroidism is a real risk.
One approach that may avoid this problem is to measure free thyroxine
and TSH levels over several weeks to months to determine if such
levels are consistent and not temporary.
subclinical hypothyroidism will avoid progression to overt hypothyroidism
and prevent the health problems associated with its effects.
It should be noted, however, that only a minority of people
with subclinical hypothyroidism will develop the active condition.
- Some studies
are showing that treating subclinical hypothyroidism improves
cholesterol level and may improve other heart functions, including
blood pressure and heart rate. (It should be noted that it is
not completely proven that subclinical hypothyroidism significantly
harms the heart or increases mortality rates.)
of subclinical hypothyroidism may improve mild symptoms, such
as impaired mental functioning and depression, although studies
are mixed on its effects on mental health. About 25% of patients
with subclinical hypothyroidism report feeling better after
taking thyroid medication even if they have not previously reported
In spite of such uncertainties, three out of four major medical
organizations recommend treatment for subclinical hypothyroidism,
particularly in the following patients with this condition:
with antibodies against thyroid factors, even if their cholesterol
levels are normal.
with infertility that may be associated with subclinical hypothyroidism.
with chronic fatigue who have normal levels of TSH may still
be experiencing autoimmune thyroid dysfunction and may significantly
benefit from treatment.
is treatment of choice for hypothyroidism. This drug is a synthetic
derivative of T4 (thyroxine), and it normalizes blood levels of
TSH, T4, and T3. Levothyroxine is slowly assimilated by body organs,
and it usually takes three to six weeks of treatment for improvement
in symptoms in adults, although many patients feel better after
two to three weeks of treatment. Usually early on they experience
weight loss, less puffiness, and improved pulse; improvements in
anemia and skin, hair, and voice tone, however, may take a few months.
Other conditions, such as goiter and high LDL cholesterol levels
decline even more gradually. (HDL levels, the so-called good cholesterol,
are not affected by treatment.)
Brand Name Versus Generic
brands available in the US and overseas include Synthroid,
Unithroid, Levothroid, Levoxyl, and Euthyrox. Synthroid is
the oldest brand. Generic brands are also available.
In the past, manufactures of levothyroxine have not had to
meet as strict standards as in the production of other drugs.
This has resulted in thyroid products with varying quality.
The FDA now has stronger requirements and has required that
all brand products, including Synthroid, resubmit applications
as new drugs. Unithroid is now approved under the new guidelines.
Some consumer groups urge that Synthroid be withdrawn until
it has completed its review.
Many expert groups, however, including the American Association
of Clinical Endocrinologists and the Thyroid Society, still
recommend the branded preparations, including Synthroid, which
has been used for over 40 years. Physicians in these organizations
argue that Synthroid has proven to be safe over its long history
and should be allowed to be manufactured during the approval
Under considerable debate is the question of whether generic
thyroid preparations, although less effective, are as effective
as brand products in any case. In some generic brands, the
amount of T4 is outside the FDA range, which can be significant.
In addition, brand-name products come in up to 12 different
strengths, while generics have less variety from which to
choose. This makes it difficult for patients whose dosages
must be frequently adjusted.
Desiccated or dried powdered thyroid (Armour Thyroid, S-P-T,
Thyrar, Thyroid Strong) is made from animal glands. It was
once the most common form of thyroid therapy but is no longer
recommended because potency varies. Some people argue that
with stricter FDA regulations, this natural form is better
controlled and may even reduce the risk of developing autoimmunity
factors. However, studies need to be conducted to confirm
Appropriate Dosage Levels. Initial dosage levels are determined
on an individual basis:
maintenance dose for most patients averages 112 micrograms, some
patients fail to feel significantly better at that level. Unfortunately,
higher doses suppress TSH levels to the point that there may be
a higher risk for osteoporosis and heart problems. Normal thyroxine
treatments do not appear to pose such risks. (One promising solution
for such patients requiring TSH suppressive treatment may be a combination
of a lower-dose thyroxine and triiodothyronine, the other important
thyroid hormone. [ See below.]
- Some patients
can begin by taking full replacement doses of thyroid hormones.
Young adults with a short history of hypothyroidism might be
able to tolerate a full initial dosage.
- Most individuals,
particularly older adults, need to build up gradually. In uncomplicated
cases, the dose typically starts at 50 micrograms per day, which
then increases in three- to four-week intervals until levels
are between 100 and 150 micrograms.
women with hypothyroidism may require higher than normal doses.
Daily Regimen. Because thyroid replacement is usually life-long,
setting up a regular daily routine is helpful. Here are some tips
Thyroid failure is an ongoing process and so is its treatment.
Many factors, such as changes in health or brands, require changing
dosages. Experts recommend that patients be reevaluated six months
after normal TSH levels have been reached and then once a year.
A dose of thyroid medication that is appropriate for a patient one
year may be too low the next. To maintain normal thyroid levels,
some patients may need to take gradually increasing doses of thyroid
hormone every year or two. If the patient changes dose levels or
thyroxine brands then he or she should be checked at least six weeks
following such changes.
a habit of taking the medication at the same time each day may
help prevent missed doses.
is very forgiving, however. The hormone remains in the body
for several days, so one missed dose should not cause a noticeable
decline in well-being. The patient can safely take two doses
the next day.
levothyroxine can be taken at any time of day either with or
without food, fiber and common daily supplements, such as calcium,
may interfere with thyroxine absorption. Some experts recommend
taking thyroid hormone upon awakening and at least 30 minutes
before consuming anything, including breakfast or supplements.
Encountered with Levothyroxine Treatment
is identical to the thyroxine the body manufactures, side effects
are nearly unheard of. Over- or under-dosing, however, is fairly
common, although rarely serious in the short term. [ See Table
Symptoms of Under- and Over-Dosing.]
of Under- and Over-Dosing of Levothyroxine
Heart symptoms. (Rapid heart beat, palpitations, and wide
variations in pulse. Possible angina.)
Agitation. (Tremor, nervousness, insomnia, excessive sweating.)
Pain. (Headache and muscle pain.)
Intestinal and metabolic symptoms. (Change in appetite, diarrhea,
Fever and intolerance to heat.
Effects of Underdosing. If the levothyroxine dose is not
sufficient to restore normal thyroid levels, or if the patient frequently
forgets to take the medication, the patient may continue to experience
symptoms of hypothyroidism. [ See Table Symptoms of Under-
and Over-Dosing.] Even mild hypothyroidism without any symptoms
can eventually lead to an increase in cholesterol levels. In one
2000 study, 40% of people taking thyroid medication still had abnormal
levels of TSH. To avoid these problems, patients should take the
proper dosage of levothyroxine as prescribed and have regular check-ups
that include measurement of blood TSH.
Effects of Overdosing: Thyrotoxicosis. Overdosing can cause
thyrotoxicosis, the symptoms of hyperthyroidism. [ See
Table Symptoms of Under- and Over-Dosing.] A patient with too
much thyroid hormone in the blood is at an increased risk for abnormal
heart rhythms, rapid heartbeat, and possibly a heart attack if the
patient has underlying heart disease. Excess thyroid hormone is
particularly dangerous in newborns, and their drug levels must be
carefully monitored to avoid brain damage.
Effects of Long-Term Treatment. Patients with hypothyroidism
usually receive life-long levothyroxine therapy. Patients without
symptoms should be monitored regularly for signs of hypothyroidism.
Studies indicate that postmenopausal women who are taking long-term
normal replacement thyroxine have no out-of-the-ordinary risk for
osteoporosis, which may be a risk with suppressive thyroid therapy.
[ See Effects of Suppressive Thyroid Therapy below.]
Some women who are taking hormone replacement therapy (HRT) to prevent
osteoporosis should ask their physician about a 2001 study that
suggested that they might need higher doses of thyroxine. In the
study, higher estrogen levels appeared to bind thyroxine throughout
the body, leaving less free thyroxine available. In women with hypothyroidism,
this could place additional demand on the thyroid. Women on HRT
might also ask their physician about alternative preventive approaches
for both heart disease and osteoporosis. [For more information see
the report # 40, Menopause, Estrogen Loss
and Their Treatments. ]
Effects of Suppressive Thyroid Therap y. Suppressive
thyroid therapy is a treatment that is high enough to block the
production of natural TSH but too low to cause hyperthyroid symptoms.
Often patients being given suppressive treatment have thyroid cancer
or thyroid nodules, such as nodular goiter.
Studies have shown that postmenopausal women taking suppressive
thyroid therapy are at risk for accelerated osteoporosis, a disease
that reduces bone mass and increases risk of fractures. Some researchers
suggest, however, that such bone loss does not significantly increase
the danger for fracture and the cholesterol-lowering benefits of
suppressive therapy outweigh this small risk. ( Premenopausal
women or men taking suppressive therapy do not appear to have the
same risk for osteoporosis, although more research is needed to
Bone density loss can be reduced or avoided by taking no higher
a dose of thyroxine than necessary to restore normal thyroid function.
In any case, doses of T4 must be continuously and carefully tailored
in all patients to avoid adverse effects on the heart. (Of note
was a 2000 study reporting that radioactive iodine may be an effective
alternative for patients with benign goiters and may have fewer
A number of medications are also available that can help preserve
bone in postmenopausal women. Note, however, that women who take
hormone replacement therapy may need to increase thyroid hormone.
[For more information see the Report #40,
Menopause, Estrogen Loss, and Their Treatments .]
Drug Interactions with Levothyroxine. Many substances and
conditions interact with levothyroxine, however, which may either
enhance or interfere with absorption. Large amounts of dietary fiber
may also reduce its action. People whose diets are consistently
high in fiber may require larger doses of the drug. Since thyroid
hormones regulate the metabolism and can affect the actions of a
number of medications, dosages may need to be adjusted if a patient
is being treated for other conditions. Even changing thyroxine brands
can have a different effect.
and Levothyroxine Combination
(T3), the other important thyroid hormone, is not ordinarily prescribed
except under special circumstances. Most patients respond well to
thyroxine alone, and the use of T3 may cause disturbances in heart
rhythms. Some patients treated only with thyroxine, however, do
not feel completely well. In one study, patients were given a regimen
that combined liothyronine (Cytomel, Triostat), a synthetic form
of triiodothyronine, and a slightly lower-than-normal dose of levothyroxine.
Patients given the combination treatment reported a better mood
and experienced fewer adverse physical symptoms. These improvements
occurred without suppressing TSH, a risk factor for osteoporosis.
The study was small, however, and patients were severely hypothyroid
and may have been lacking T3 in the first place. The study also
was only ten weeks long. More work is needed before this combination
is recommended widely.
People with hypothyroidism
have higher than normal levels of homocysteine, an amino acid that
is a suspected risk factor for heart disease. Vitamins B6, B12,
and folic acid (another vitamin B) are important in protecting against
elevated blood levels. Supplements, then, may be important companions
to thyroid replacement in restoring normal homocysteine levels.
of Special Cases
Elderly and Patients with Heart Disease. Elderly patients and
those with hypothyroidism and heart conditions usually start with
lower doses, since a large initial dose may be a shock to the heart,
and about 40% of patients who have heart disease must take a lower-than-average
maintenance doses. Thyroid treatment may aggravate angina in about
one-fifth of patients with the heart condition. The hormone has
no effect and may even improve angina in the remaining four fifths.
It should be noted that experts do not recommend treatment for subclinical
hypothyroidism in elderly patients with heart disease whose test
show only minimal thyroid hormone abnormalities and who have no
anti-thyroid antibodies. Such patients should be closely monitored,
Preliminary research indicates that in patients undergoing cardiac
bypass surgery, administration of triiodothyronine at the time of
surgery may improve blood flow, heart rate, and cardiac output.
Patients with advanced heart failure may also benefit from supplementary
Of some importance was a 2000 study that suggested many elderly
patients who have been treated for hypothyroidism for years may
not really need the medication. In the study, half the patients
taking thyroid hormone were taken off the medication successfully.
Many of these patients may have been inappropriately diagnosed years
ago, when testing was less accurate.
Treating Newborns and Infants with Hypothyroidism. Newborns
with congenital hypothyroid should be treated as soon as possible
to prevent mental deficiency, poor growth, and abnormal development.
Treating the infant after about a month and a half does not reverse
any existing mental impairment, although it does reverse physical
damage. Some experts urge treating newborns within two weeks of
birth and at slightly higher than recommended doses, although evidence
is lacking to confirm these recommendations. Single oral doses of
levothyroxine can usually restore normal thyroid hormone levels
within one to two weeks. Infants should be monitored closely to
be sure that thyroxine levels are as consistently close to normal
as possible. These children need to continue life-long thyroid hormone
One study suggested that breast-fed babies with congenital hypothyroidism
may test slightly better later on than bottle-fed infants. Soy-based
formulas can reduce the intestinal absorption of thyroxine. If soy
formula is introduced, the hormone dose should be increased, and
when the formula is discontinued the thyroid dose should be reduced.
Treatment during Pregnancy and for Postpartum Thyroiditis.
Women who have hypothyroidism before becoming pregnant may need
to increase their dose of levothyroxine during pregnancy. In very
rare cases, women may actually develop hypothyroidism while pregnant
and need to be treated with levothyroxine in full replacement doses
to reduce the risk of stillbirth. The developing baby is not affected
when the pregnant woman takes thyroid hormones. The pregnant woman
with hypothyroidism should be monitored regularly and doses adjusted
as necessary. If postpartum thyroiditis develops after delivery,
any thyroid medication should be reduced or temporarily stopped
during this period.
Treatment for Myxedema Coma. Myxedema coma is an emergency
situation and the patient should be given intravenous doses of thyroid
hormone, which could be triiodothyronine, levothyroxine, or both.
Lower doses may be safer in elderly patients. Often, hydrocortisone,
a corticosteroid, is also administered. Any other accompanying critical
condition, including low body temperature, slow heart rate, low
blood sugar, and difficulty in breathing, should also be treated
Treating Iodide Deficiency. People who are iodide deficient
may be able to be treated with iodized salt. The current RDA is
now 150 micrograms for both men and women, with an upper limit of
1100 micrograms to avoid thyroid injury. In addition to iodized
salt, seafood is a good source. Except for plants grown in iodine-rich
soil, most other foods do not contain iodine. According to a 2000
study, when iodide-deficient children are given iodized salt, simply
increasing the iodide levels improves their mental status, even
if their iodide levels are still below normal. Another African study
reported that when iodine replacement reduced hypothyroidism rates
in areas where food supplies were low, the population's energy levels
and fertility increased. This then placed a higher burden on already
low resources. Experts warn that while it is important to improve
nutritional levels in developing countries, all concerns must be
addressed. Although hypothyroidism from iodine deficiency is still
very uncommon in nations where iodine has been added to salt, the
consumption of iodized salt has declined over the past decades.
In addition, iodine levels have been reduced in animal feed and
bread products. Experts believe this may be causing an increase
in subclinical hypothyroidism (without symptoms) even in developed
Treatment of Secondary Hypothyroidism. The small percentage
of patients who have hypothyroidism due to a pituitary or hypothalamus
problem should take levothyroxine along with their other medication
to treat the primary disorder. In secondary hypothyroidism, the
adrenal gland is often impaired. This means that the increased activity
in the metabolic rate that occurs after thyroid replacement therapy
may trigger a severe and even life-threatening condition called
addisonian crisis, which is caused by a sudden demand for the depleted
stress hormones secreted by the adrenal gland. Before administering
thyroid replacement, then, the physician should initiate a test
that stimulates release of ACTH, one of the hormones secreted by
the adrenal gland. If there is insufficient ACTH, then before thyroid
replacement is started, the patient is usually treated with cortisone
acetate, a stress hormone.
Thyroid Hormone Inappropriately
In one study
of those taking thyroid hormone, 12% of women and 29% of men were
taking it inappropriately. In some cases of infertility, women with
menstrual problems and repeated miscarriages and men with low sperm
counts have been treated with thyroid hormones even where there
was no evidence of thyroid abnormalities. (Women showing high levels
of TSH, however, may benefit from levothyroxine therapy.) Other
inappropriate uses for thyroid hormones are for weight loss and
to reduce high cholesterol levels. Thyroid hormones have also been
given to treat so-called metabolic insufficiency. Vague symptoms
suggesting low metabolism, such as dry skin, fatigue, slight anemia,
constipation, depression, and apathy, should not be treated indiscriminately
with thyroid hormone. No evidence exists that thyroid therapy is
beneficial unless the patient has proven hypothyroidism. Use of
thyroid hormones can weaken muscles and over the long term, even
heart muscles. One exception is the use of thyroxine to enhance
drugs used for the treatment of severe depression.
ELSE CAN INFORMATION ABOUT HYPOTHYROIDISM BE OBTAINED
The Thyroid Society,
7515 South Main Street, Suite 545, Houston, TX 77030. Call 1-800-THYROID
or (713-799-9909) or on the Internet (https://www.the-thyroid-society.org).
The society offers excellent in-depth information. They also have
local listings of physicians well versed in thyroid disease.
Thyroid Foundation of America, Inc., 350 Ruth Sleeper Hall-RSL350,
40 Parkman St, Boston, MA 02114. Call (800-832-8321) or on the Internet
The foundation provides local listings of physicians qualified to
treat thyroid disorders and will send an information package.
The Endocrine Society, 4350 East West Hwy, Ste 500, Bethesda, MD
20814-4110. Call 301-941-0200 or on the Internet (https://www.endo-society.org/).
The society provides one-page fact sheets on thyroid and other endocrine
American Thyroid Association, PO Box 1836, Falls Church, VA 22041-1836.
Fax 703-998-8893 or on the Internet (https://www.thyroid.org/).
The association will provide information about common thyroid diseases,
including a booklet on both hypothyroidism and hyperthyroidism.
The association will also provide local listings of physicians who
have an interest and experience in treating patients with thyroid
Thyroid Foundation of Canada, PO Box/CP 1919 Stn Main, Kingston,
ON K7L5J7. Call (613-544-8364) or In Canada: (800-267-8822), on
the Internet (https://www.thyroid.ca)
American Association of Clinical Endocrinologists, 1000 Riverside
Ave., Ste 205, Jacksonville FL 32204. Call (904-353-7878) or on
the Internet (https://aace.com).
Web site provides names of local endocrinologists.
Good Internet Site on Thyroid