Women who take birth control pills might
be at increased risk for a long-term loss of sexual desire,
according to new research from a team at the Lahey Clinic
in Boston.
"We have known for a long time that 30 to 40 percent
of women on birth control pills have decreased libido,"
said study co-author Dr. Andre Guay, director of the Center
for Sexual Function/Endocrinology at the clinic.
But his findings, published in the January issue of The
Journal of Sexual Medicine, showed that lowered testosterone
levels caused by use of birth control pills can persist
for up to a year after a woman stops taking them. And
that, in turn, may lower her sexual desire, along with
her ability to get aroused and become lubricated.
Birth control pills decrease circulating levels of androgens,
which modulate sexual functioning, Guay wrote in the report.
In women, testosterone is made in the ovaries and in the
adrenal glands. When a woman is on the pill, androgen
production in the ovaries is inhibited and the production
of a protein called sex hormone-binding globulin (SHBG)
goes up. The combination leads to lower circulating levels
of testosterone, Guay said.
Guay and his team studied 124 premenopausal women who
had sexual health complaints for more than six months.
Within the group of 124, they looked at three subgroups:
those who had been on birth control pills for more than
six months and kept taking it, those who had been on birth
control pills for more than six months and stopped, and
those who had never taken birth control pills.
The average ages in the groups were similar: 32, 33 and
36.
They did blood tests to measure production of SHBG, a
protein made by the liver that binds to testosterone.
"When you put someone on the birth control pill, you block
a lot of the ovarian production [of testosterone]," Guay
said. Levels of SHBG are high in women taking oral contraceptives
and in women during their late stages of pregnancy.
The team found that the SHBG values in the women who
continued using birth control pills were four times higher
than those who never used it. And even though the SHBG
values went down after women stopped using birth control
pills, the levels in those who discontinued remained high
compared to the levels of those who never used them.
Eleven women were followed for a year or longer after
they stopped taking birth control pills, and at a mean
length of about 11 months after quitting, their SHBG was
about double the level of never-users.
"If that binding protein is still a bit elevated, you
might have a decrease in libido that persists," Guay said.
"Beyond a year, we don't know [what happens]," said Guay.
"The question is, does the birth control pill imprint
on the body a signal to continue making this protein that
attaches to the testosterone? If so, these women would
have less testosterone."
"Right now, this is an observation," he added. "Now the
question is, 'Does this mean that the women who have had
been on birth control pills would have sexual dysfunction
symptoms down the road?'"
"It's an observation no one else has made before and
we are not sure of the clinical significance," he said.
Another expert called the findings "a lot of fuss about
nothing."
"This is not a surprise," said Dr. Richard Spark, director
of steroid research at Beth Israel
Deaconness Medical Center. "I think people have known
about this for years We've known that estrogen acts on
the liver to stimulate SHBG production."
Based on the results, Spark said, he doesn't think women
should be concerned.
