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Some women with very low body fat - such as athletes and professional dancers - stop menstruating and have an increased risk of bone fracture. Now, there's increasing evidence that hormone treatments can help these women.

The study involved young women with extremely low body fat and a condition called hypothalamic amenorrhea. It's part of a self-preservation mechanism shared by many species: when the food supply is low, scarce energy is focused on survival, not reproduction.

"These women had stopped having their periods because they were exercising more than usual, or having stress, or a little bit of decreased food intake," says Sharon Chou, a researcher at Beth Israel Deaconess Medical Center in Boston.

In a new study, she and her colleagues tested whether a synthetic form of the hormone leptin could restore normal menstrual periods.

Leptin was discovered in 1994. It is related to the body's reserves of fat, so the hormone was investigated as a possible treatment to curb the appetites of obese people. That didn't work, but subsequent research found that leptin does play an important role in regulating how the body responds to lower food supplies.

Researchers found women with hypothalamic amenorrhea had low levels of leptin, and a 2004 study suggested that treatments with synthetic leptin (metreleptin) could restore menstruation. This latest research confirms that finding with a larger, more scientifically-rigorous study.

Nevertheless, Chou says the research is still a work in progress, so doctors won't be doing leptin treatments in the immediate future.

"But the idea is, these women can regain their menstrual cycle, menstrual function. And then, we're also looking to see if, used over a longer time period - perhaps one or two years - if these women would regain some of their bone loss."

The paper describing the effectiveness of leptin treatments by first author Sharon Chou, senior author Christos Mantzoros, and colleagues, is published online in the Proceedings of the National Academy of Sciences.

menstruate: when a woman menstruates, there is a flow of blood from her womb, usually once a month 行經；來月經

hypothalamic: 下丘腦

amenorrhea: 閉經；月經不調

leptin: a protein produced by fatty tissue and believed to regulate fat storage in the body 瘦素

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（來源：VOA 編輯：崔旭燕）