Estrogen, Not Just Testosterone, Responsible For Male Sex Drive

Michael Harper for – Your Universe Online

It’s not just a lack of testosterone – the hormone commonly associated with manliness -which can cause middle-aged men to gain weight and lose their sex drive. According to a new study by researchers at Massachusetts General Hospital, a drop in estrogen levels can also leave these men feeling flabby and less than amorous.

Testosterone has long been thought to be the culprit for a perceived stronger sex drive in men than in women. Yet this new study, published in the latest edition of the New England Journal of Medicine, finds that estrogen may also be responsible for guiding men’s sex drives.

It’s long been known that the body converts estrogen into testosterone, but this study furthers this understanding and casts a larger role for estrogen in the overall sex drive of men. Joel Finkelstein is an endocrinologist at Massachusetts General Hospital and authored this groundbreaking new study of hormones and sexuality.

“This study establishes testosterone levels at which various physiological functions start to become impaired, which may help provide a rationale for determining which men should be treated with testosterone supplements,” explains Finkelstein in a statement to the AFP.

“What will surprise many people is that loss of sexual desire in men with low testosterone is due to lack of estrogen.”

As men get into their 30s and 40s, their testosterone levels begin to drop, diminishing their muscle mass, reducing their sex drive and adding stubborn pounds to their midsections. Drug companies have successfully capitalized on this natural condition and labeled the transition “low T syndrome” in efforts to sell testosterone supplements to these men.

After studying nearly 300 healthy men, Finkelstein and his research team found that increases in estrogen were more responsible for the weight gain than decreases in testosterone levels.

The study participants were between the ages of 20 and 50, and were given supplements meant to suppress both hormones. Afterwards, half of the men were given either a testosterone-boosting gel or a placebo. The second group of men were given the testosterone gel and a drug which further lowered the production of estrogen.

After receiving this battery of hormone therapy, the volunteers in the first group saw the same kind of increase in their body fat normally indicative of low testosterone levels. Any further reduction in lean body mass, such as shrinking thigh muscles and overall strength, didn’t occur until testosterone levels became much lower. As the male hormone continued to drop, so too did the sexual drive of the men in the first study group. These men were still able to achieve an erection, however, until their testosterone levels reached their lowest points.

The second group of men who had their estrogen suppressed also saw increases in body fat and decreases in lean body mass, but their sexual drives were more affected than those men in the first group. Observing these results, Finkelstein now believes estrogen is more closely related with a man’s sexual drive, while testosterone is mainly responsible for a reduction in lean body mass and weight gain.

These findings could change the way some pharmaceuticals target men looking to increase their sex drive through hormone therapy. Though Finkelstein’s research has pointed out that estrogen might be a better way to boost a man’s sex drive, he also warns that increasing this hormone could lead to other, potentially negative side effects.

“We also need to look into how testosterone replacement therapy would effect prostate health – both prostate cancer and the prostate enlargement that causes unpleasant symptoms in many older men – and heart disease,” Finkelstein said.