"I think the question that arises is how much of this is related to hormones and how much of it is the facts of life that we experience as we age," said Dr. Thomas Walsh, an assistant professor and director of male reproductive and sexual medicine at the University of Washington's School of Medicine in Seattle.
"There is still a lot of controversy, and I don't think we have all the answers yet. You have to take the data at hand and apply it to the individual," he said.
Up to four million men may have low testosterone, with most caused by age-related declines. However, only a minority receive treatment, according to Walsh. That number of men affected is expected to rise.
The female misnomer
'Male menopause' may grab attention, but experts dislike the term, because it glosses over the significant differences between the hormonal changes men and women experience as they age.
"Nobody doubts female menopause, and nobody doubts the mechanism by which it happens, that's not the case for male menopause," said Dr. Ike Iheanacho, editor of the journal Drug and Therapeutics Bulletin. "That epithet is unhelpful, because it deters people from doing what we [have] done, which is look at the evidence."
The review, which reflected the journal's opinion, found weak causal evidence that age-related hormone declines cause symptoms in men, a lack of long-term data, and at best, mixed results for short-term treatment.
For a woman, menopause marks the end of fertility and occurs when progesterone and estrogen, produced by the ovaries, drop off. Symptoms can last several years, according to the U.S. National Institutes of Health (NIH). Hormonal changes in men are quite different. Testosterone levels can decrease by about 1 percent to 2 percent each year after about the age of 40. While menopause is a universal experience for women, testosterone does not decline in all men. Other factors besides aging, like obesity or injury, are associated with low testosterone.
For many years, long-term hormone replacement for women was considered protective, that is until study results in 2002 revealed it increased risks of heart disease, stroke, blood clots and breast cancer, according to the NIH.
This history has implications for men with low hormones and symptoms, Walsh said. "You are seeing today far more caution on the part of clinicians and investigators."
Two papers published in the July issue of the New England Journal of Medicine addressed the diagnosis of hypogonadism and its treatment.
In one study, researchers led by Frederick Wu of the University of Manchester used data from 3,369 European men to find correlations between testosterone levels and a battery of potential symptoms. As a result, they suggested that the presence of at least three measures of sexual dysfunction, including frequency of thoughts about sex and erectile function, in a man with a testosterone level below 11 nanomoles per liter could be used to define late-onset hypogonadism. (The study defined a decreased level as between 13 and 8 nanomoles per liter for total testosterone.) However, these symptoms were also widely reported by men who did not suffer from depressed hormone levels.
This causal relationship between hormone levels and symptoms is always a question, according to Dr. William Bremner, chairman of the department of medicine at the University of Washington's School of Medicine, who wrote about that research in an editorial in the journal.
"In truth you don't know that those are due to the testosterone until you give men testosterone and see whether those symptoms are improved," he said. The problem is, men taking testosterone experience an unusually high rate of cardiovascular problems.
The Women's Health Initiative Study, which revealed risks of hormone replacement therapy, followed a total of 161,808 women over 15 years. No long-term research like this has been conducted in men, but it is needed, Bremner said.
There are more natural methods rather than man-made testosterone. An Austrian study found testosterone is boosted by sunbathing and vitamin D.
There is also a lifestyle connection. Low testosterone is associated with obesity, diabetes and metabolic syndrome – a combination of disorders linked to diabetes and cardiovascular disease. All three are on the rise within the United States, according to data from the Centers for Disease Control.