Men, as they age, are frequently diagnosed as having a deficiency in the hormone testosterone, referred to as the "male sex hormone." Now studies suggest that, surprisingly, it may instead be an issue of estrogen. The notion that testosterone is male and estrogen is female is a vast oversimplification; men and women both have both types of hormones. In fact, testosterone turns into estrogen as it is used by the male body. Men do have far higher amounts of testosterone than women do, but a study published earlier this month suggests that the symptoms attributed to low testosterone—including reduced sex drive, lowered energy, increased body fat and reduced muscle mass, and a down mood—are actually due to low levels of estrogen.
The symptoms are not dissimilar to those of menopause, so it isn’t particularly odd that they have substantially the same cause; menopause is marked by a drop in estrogen production. However, the degree to which estrogen affects signs of aging in men has proven to be much greater than suspected. In the study, volunteer subjects who did not convert testosterone to estrogen developed more body fat than those in whom this process was not disrupted. The changes in sexuality—reductions in both drive and capability—turned out to be linked to levels of both testosterone and estrogen.
Another effect of the reduction in estrogen production is memory lapses and cognitive deficits, one reason there deficits are so common in old age. A recent study explored the exact nature of the relationship between the sex hormones and the brain. Dementia and other cognitive effects of aging are most visible in a region of the brain called the hippocampus, which suffers the ravages of time particularly strongly. The researchers found that estrogen helps form memory in the presence of another compound.
This research has important implications for treatments for menopausal symptoms and age-related cognitive decline. Hormone replacement therapy is given to women after menopause to treat their symptoms, but there are dangerous and sometimes lethal side effects, such as an increased risk of cardiovascular disease. Researchers are hoping to be able to separate out the helpful compounds to improve cognitive function in these patients without those side effect risks.