Pot Belly, Low Sexual Desire in Middle-aged Men Linked with Lower Estrogen Levels

A drop in estrogen levels along with testosterone decrease is responsible for lower sexual functioning and decreased strength in middle-aged men, reports a study from Massachusetts General Hospital.

Until recently, physicians believed that decrease in the male sex hormone was linked with declining sexual function in men. Now, researchers have found that even female sex hormone "estrogen" is linked with developing a pot belly, a low sexual desire and erectile dysfunction in older men.

".. the biggest surprise [of the study] was that some of the symptoms routinely attributed to testosterone deficiency are actually partially or almost exclusively caused by the decline in estrogens that is an inseparable result of lower testosterone levels," said Joel Finkelstein, MD, of the MGH Endocrine Unit, corresponding author of the study.

Estrogen in males is produced when an enzyme called aromatase converts a small amount of testosterone into the female sex hormone. Therefore, any drop in testosterone automatically leads to a decline in estrogen levels.

Researchers in the current study wanted to find out whether all physical problems in men linked to hormonal changes are due to testosterone or estrogen or both.

For the study, the scientists gave participants a drug that suppressed production of reproductive hormones. Men in the first group were randomly given either various doses testosterone gel or placebo. Men in the second group were also given similar doses of testosterone and aromatse inhibitors, which prevented the testosterone from being converted to estrogen.

About 150 men in each group completed the test. Study participants were also asked to complete monthly blood tests along with answering questionnaires about the physical and sexual health. The current study was conducted under controlled conditions where researchers regulated the production of hormones. Researchers said that they'd want to test the model in older men.

Study results showed that the first set of men, where researchers hadn't reduced the production of estrogen, had increased body weight and decrease in sexual function. These symptoms were similar to those seen in men who have mild level of testosterone deficiency. The second group, which had lower estrogen levels along with testosterone levels, had major changes in sexual and physical health.

Researchers found that testosterone regulated lead body mass, strength and muscle size while estrogen regulated body fat composition and sexual function.

Male hypogonadism is a condition where the male sex organs fail to produce enough hormones for the body to function, which results in changes in physical and sexual health. Doctors generally look just for a drop in testosterone levels before prescribing treatment for the condition.

Experts of the study argue that certain functions in men are actually regulated by estrogen, which is why doctors need to look at specific symptoms before beginning treatment.

"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," said Finkelstein, who is an associate professor of Medicine at Harvard Medical School, according to a news release. "In light of what the Women's Health Initiative discovered about the unexpected effects of estrogen replacement therapy in women, we need a Men's Health Initiative to investigate those questions before large-scale testosterone replacement can be recommended."

The study is published in the journal New England Journal of Medicine.