The “Missing Link” to Restore Fertility in Lean Women

More and more women are shedding pounds as they mimic celebrities without realizing that dramatic weight loss could damage their prospects of becoming pregnant.

Super-slim women who diet too much or exercise too much may have too little body fat to have a baby.

In addition to reducing body fat, strenuous exercise may disrupt the normal fluctuation of hormones in the menstrual cycle and interfere with menstruation or ovulation.

Besides a moderate exercise program balanced by adequate calorie intake, these women may also be able to restore their fertility by taking a synthetic version of leptin.

Leptin is a hormone that plays a key role in regulating energy intake and energy expenditure, including appetite and metabolism.

Mostly it’s been studied as a possible way to suppress the appetites of overweight people, but Harvard researchers examined leptin’s role from the opposite end of the energy spectrum by studying individuals with extremely low levels of body fat.

A new study reported on-line this week in the Proceedings of the National Academy of Sciences suggests leptin has a role in improving faulty hormone signaling when levels of body fat are extremely low.

The double-blind, placebo-controlled trial included 20 young, slim women, mostly college-age, mainly runners, who watched their diets and appeared healthy. But they had abnormal hormone levels, had ceased menstruating, and had stopped ovulating, said senior author Christos Mantzoros, MD, Dsc, Director of the Human Nutrition Unit at BIDMC and Professor of Medicine at Harvard Medical School, in a press release.

Over 9 months, the women were given either a synthetic form of leptin (known as metreleptin) or a placebo in daily under-the-skin injections.

The replacement leptin resulted in significantly elevated levels of the hormone within just a month of treatment; 7 of 10 women began to menstruate and 4 of the 7 began ovulating, he said.

Dr. Mantzoros calls leptin the “missing link” in women with significantly diminished body fat that, in turn, leads to hormonal abnormalities.

The synthetic version may just be a good solution for the more than 30% of women of reproductive age who do not menstruate due to hormonal problems, particularly those with low body fat levels.

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