Lack of estrogen leads to middle-aged spread in men
The female sex hormone plays a much bigger role as men age, with low levels leading to middle-aged spread and loss of desire
It is the scourge of many a middle-aged man: He gets a pot belly, uses lighter weights at the gym and just doesn't have the sexual desire of his younger years.
The obvious culprit is testosterone, since men make less of the male sex hormone as years go by. But a surprising new answer is emerging, one that doctors say could reinvigorate the study of how men's bodies age. Estrogen, the female sex hormone, plays a much bigger role in men than previously thought. Falling levels contribute to expanding waistlines in both sexes.
Some of the symptoms routinely attributed to testosterone deficiency are actually partially or almost exclusively caused by the decline in estrogens
The discovery of the role of estrogen in men is "a major advance", said Dr Peter Snyder, a professor of medicine at the University of Pennsylvania, who is leading a research project on hormone therapy for men over 65.
Until recently, testosterone deficiency was considered nearly the sole reason that men underwent the familiar physical complaints of midlife. The new frontier of research involves figuring out which hormone does what in men, and how body functions are affected at different levels.
While dwindling testosterone levels are to blame for middle-aged men's smaller muscles, falling levels of estrogen regulate fat accumulation, according to a study published in the New England Journal of Medicine, which provided the most conclusive evidence to date that estrogen was a major factor in male midlife woes. Both hormones are needed for libido.
"Some of the symptoms routinely attributed to testosterone deficiency are actually partially or almost exclusively caused by the decline in estrogens," said Joel Finkelstein, an endocrinologist at Harvard Medical School and the study's lead author.
His study is only the start of what many hope will be a new understanding of testosterone and estrogen in men. Snyder is leading another study, the Testosterone Trial, which measures levels of both hormones and asks whether testosterone treatment can make older men with low testosterone levels more youthful.