Ask the Doctors: Studies show possible link between FSH, weight gain

Dear Doctor: I recently read that blocking follicle-stimulating hormone can combat post-menopausal bone loss and weight gain in women. Please tell me how to go about blocking that hormone!

Dear Reader: Talk to women who have hit the age of 45 and beyond, and they pretty much agree that maintaining their weight, let alone losing weight, seems much harder than when they were younger. Now a series of studies have put follicle-stimulating hormone, or FSH, into the spotlight.

Produced by the pituitary gland, FSH plays a role in the release of eggs in women and the production of sperm in men. When a woman approaches menopause, the time at which her ovaries cease functioning, her blood levels of estrogen drop and FSH spikes. At this same stage of life, women begin to experience bone loss.

A professor at a medical school in New York City was intrigued by the fact that, even when estrogen levels held steady, bone loss continued to occur. As a result, he began to wonder whether FSH levels might play a role in the effects of menopause. Although he was studying the role of FSH in bone loss, he was startled when fat levels and weight gain were affected as well.

In a series of experiments using mice whose ovaries had been removed, researchers administered an antibody to block FSH. Without ovaries to produce estrogen, which prevents bone loss, the mice should have experienced a drop in bone mass. Researchers were surprised to find that not only did the bone mass of the mice hold steady, they also began to lose fat.

A colleague at another medical center was persuaded to try the same experiment and got the same results. They also advanced their understanding of how and why the mice, despite being forced into menopause, experienced weight loss.

To get into the details, we first need to talk about two types of adipose tissue — white and brown fat. Unlike white fat, whose job is to store energy for future use, brown fat is loaded with mitochondria, tiny structures within our cells that burn energy and give off heat.

As babies and children, we have plenty of brown fat. By the time we hit adulthood, only small amounts of brown fat remain. In the case of the FSH-deprived mice, their levels of brown fat rose. This caused their metabolism to rev up, burn calories and lose weight.

Considering that women typically gain anywhere from 5 to 15 pounds or more as a result of menopause, with much of it around the abdomen, it’s easy to see why these results have sparked widespread interest. But as the researchers themselves point out, it can be a long leap to translate results from mice to human beings. Only time and further studies will tell.

Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.