Hormone replacement therapy for men

Harvard Health Letter, Oct, 1996 by Ronny G. Frischman

If the only urge a man feels in spring is a desire to climb out of his long underwear, it's a sure sign that he's getting on in years. Although there is no elixir to reverse aging, researchers are asking whether hormone supplements might restore a more youthful outlook and bolster the quality of life for aging men.

Although sex hormone levels start to decline in midlife for both men and women, only in women has this been considered a condition that warranted medical treatment. As a result, millions of menopausal women take hormone-replacement therapy (HRT) to relieve hot flashes and other symptoms of falling estrogen levels. HRT also may lower the risk for osteoporosis, heart disease, and Alzheimer's.

In contrast, male hormone-replacement therapy (MHRT) has seldom been prescribed for healthy, older men. However, recent evidence suggests that men might be able to stay leaner, stronger, happier, and more virile longer if they took supplements to make up for the testosterone that is lost to advancing age.

With possible benefits extending from the bedroom to the boardroom, the appeal of testosterone-replacement therapy is obvious. There have been only limited scientific studies of its long-term effects, however, and experts remain concerned that hormone supplements might put mature men - who already are more vulnerable to prostate cancer and cardiovascular disease than younger fellows - at even greater risk.

Just starting out

As the principal masculinizing hormone (androgen), testosterone stimulates bone and muscle growth and promotes development of male genitalia. It begins shaping the male child in utero as early as 12 weeks into gestation and remains largely quiescent until puberty. At that point, acting on a signal from the brain's hypothalamus, the pituitary gland tells specialized cells in the testes to kick testosterone production into high gear. This hormonal surge activates sex drive and sperm production, prompts the appearance of acne, facial and pubic hair, and deepens the voice. Not exclusive to men, testosterone is produced in much smaller quantities in women.

In adult men, the testes produce about 7 mg of testosterone daily, with output generally being higher in the early morning than at other times of the day. Most testosterone travels through the bloodstream in a biologically inactive form; only 1-2% interacts with tissue. A standard blood test that measures both types is used when doctors want to assess a man's testosterone level.

Though the idea of male menopause, or male climacteric, has been tossed about for years, the fact is that hormonal shifts related to aging differ for men and women. Men simply don't undergo the dramatic "change of life" that women do. Some time in their los or 50s, women stop menstruating - their ovaries literally cease to produce eggs or estrogen. In a wild attempt to restore flagging estrogen levels and ovary function, the pituitary releases huge amounts of gonadotropin hormones. The resulting hormonal turbulence accounts for the hot flashes, mood swings, and vaginal dryness that plague many menopausal women.

A slower decline

The male sex hormone doesn't nosedive like estrogen. As men get older, the amount of testosterone in their blood gradually drops, and the peaks and valleys seen in younger men flatten out. By the age of 60, many men have testosterone levels hovering around the low end of normal. Although there is no failure in the sexual or reproductive system, the brain speaks less clearly to the pituitary gland, which in turn sends weaker signals to the testicles - where fewer cells are available to respond. Some studies suggest that men's testosterone levels may fall 30-40% from their late 40s to early 70s.

Although physiologic changes occur in men, they are generally more subtle than those in women. For instance, men may see sexual function start to slide - the machinery still operates, but with less verve than the younger model. Muscles begin to atrophy, fat collects around the middle, and bones lose their density, leaving a man more prone to osteoporosis. Just how great a role the decline in testosterone plays in precipitating these changes is unclear.

Physicians have usually reserved testosterone replacement for men who have hypogonadism, a condition in which the testicles produce an inadequate amount of the hormone. Now that more men are living into their 70s, 80s, and beyond, scientists are testing the usefulness of MHRT in those who are testosterone impoverished, if not frankly deficient. "There is a lot of enthusiasm about hormone replacement, but we have to find out if there is a downside to it," said Richard M. Spark, associate clinical professor of medicine at Harvard Medical School and director of the steroid research laboratory at Boston's Beth Israel Hospital.

Looking good

MHRT research is relatively new, and although most studies are small there are preliminary signs of benefit. In an experiment at Emory University School of Medicine in Atlanta, geriatrician Joyce S. Tenover gave injections of testosterone or a placebo to 13 men, ages 57-76, whose levels were at the low end of normal.