Women with low body fat who have stopped menstruating may be able to restore their periods and reduce their risk of bone loss by taking doses of the hormone leptin, according to a new study.

Researchers tested leptin on volunteers who had hypothalamic amenorrhea, a condition in which women cease menstruating , usually as a result of exercise, stress or a decrease in food. The condition is sometimes seen in athletic women such as runners and dancers. It can lead to fertility problems, bone loss and an increased risk for osteoporosis and bone fracture.

Of the 20 women in the study, 11 were injected with leptin, a hormone that regulates appetite, once a day for 36 weeks. The others were given a placebo. The researchers found that the women on leptin were the more likely to start menstruating again. In addition, they had biological markers in their blood that indicated new bone was forming.

Easier than gaining weight

The findings suggest leptin may be used as a treatment for hypothalamic amenorrhea. However, because the study involved so few subjects, more research would be needed to confirm the results and look at the long-term safety of the therapy, the researchers said. In addition, subjects would need to be followed over a longer period of time to confirm that leptin actually increases bone formation.

While gaining weight usually cures hypothalamic amenorrhea, the researchers noted that for some women, this is not always practical.

"Ideally, these women should probably gain weight or not exercise as much," said study researcher Dr. Sharon Chou of the Beth Israel Deaconess Medical Center in Boston. "But I think there's a lot of athletes out there where it's going to be hard to do, especially if they like to play sports or if this is what their career is."

Leptin and body fat

Natural levels of leptin in the body reflect how much energy is stored in fat cells. Too little leptin signals to the body that it is in a state of energy deficiency. Previous research had indicated that women with hypothalamic amenorrhea have chronically low leptin levels.

The new study involved women ages 18 to 35 with hypothalamic amenorrhea. They were randomly assigned to take metreleptin, a synthetic form of leptin, or the placebo. Neither the subjects nor the doctors knew which treatment the participants received. After about nine months, seven of 10 women who took metreleptin had their periods return, compared with just two of the nine who took the placebo. The 20th woman, who was taking metreleptin, dropped out of the study.

Hypothalamic amenorrhea is found in some of those with eating disorders as well as in athletes.

Chou notes that leptin can have the side effect of causing weight loss, so patients should be carefully weighed, and their dose adjusted to prevent weight loss, she said.

The study was published this week in the journal Proceedings of the National Academy of Sciences.

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