It is the scourge of many a middle-aged man: he starts getting a pot belly, using lighter weights at the gym, and somehow doesn’t have the sexual desire of his younger years.
The obvious culprit is testosterone, since men gradually 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, turns out to play a much bigger role in men’s bodies than previously thought.
“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.