Middle age is a time of hormonal upheaval for both men and women. The menopause-associated hormonal changes experienced by women are widely known. Less well-known are the changes experienced by men. Men undergo similar decreases in hormone production as women, but the decrease is more gradual. In men, the effects of decreasing testosterone levels may be compounded by an increase in estrogen production.
The testes and adrenal glands produce testosterone in men. The hormone is necessary for normal libido and sexual function. Testosterone also helps build protein and influences the production of blood cells, formation of bone, lipid metabolism, liver function and growth of the prostate gland, notes the website BodyLogicMD.
Testosterone production naturally slows as men age, usually beginning between 40 and 55 years of age. The slowdown is gradual, and most men experience no symptoms. Others, however, experience decreased sexual desire, mood changes, fatigue and lack of energy, explains BodyLogicMD. The period of declining testosterone production, called andropause, may last decades, and low testosterone levels may lead to heart disease or weakened bones.
Estrogen in Men
Along with testosterone, men also produce small quantities of estrogen throughout their lives, writes male hormone specialist Rick Cohen, M.D., on the website International Anti-Aging Systems. Men require small amounts of estrogen for a healthy heart, brain function, bones and libido. Estrogen and testosterone are held in balance, but as testosterone levels drop during middle age, estrogen production either remains steady — thus increasing the proportion of estrogen to testosterone — or estrogen levels may increase.
Causes of Increased Estrogen
Increases in estrogen production in men may result from normal aging, a high degree of body fat, hormone replacement therapy or medications, nutritional deficiencies or excessive alcohol use, Cohen states. Dropping testosterone levels worsen the hormone imbalance. When testosterone levels drop too low, as they do in older men, estrogen attaches to the receptor sites on cells that are normally occupied by testosterone. As estrogen levels continue to increase and testosterone to decrease, Cohen says, testosterone is unable to stimulate the cells. The result is decreased sexual desire and arousal.
Excessive estrogen can trigger a cascade effect that further decreases testosterone production, Cohen explains. High levels of estrogen can saturate testosterone receptors in the hypothalamus, reducing the signal sent to the pituitary gland. The pituitary gland responds to the reduced signal by producing less of a precursor hormone needed by the testes to produce testosterone. Hormone imbalance also reduces the amount of free testosterone circulating in the body, which means less testosterone is available to attach to cell receptor sites. High estrogen levels in men may eventually lead to diabetes or heart disease, Cohen notes, based on research published in The "American Journal of Medicine." Hormone replacement therapy can relieve the symptoms of hormone imbalance, suggests Penn State College of Medicine. Side effects of hormone replacement therapy may include prostate disease, liver toxicity or an abnormal increase in red blood cells.