Women with the eating disorder anorexia nervosa generally have low levels of the predominantly male hormone testosterone, a study in 217 women found. Results of the study will be presented Sunday, June 3, at The Endocrine Society’s 89th Annual Meeting in Toronto.

Many people think of testosterone as a male hormone, but it is present in small quantities in women. This hormone plays an important role in maintaining healthy bones and muscle mass in men, and according to the study’s lead author, Dr. Karen Miller, there is increasing evidence that it does in women as well. An endocrinologist at Harvard-affiliated Massachusetts General Hospital, Miller said less than 15 percent of women with anorexia nervosa have normal bone density.

Miller and her colleagues studied 169 women with anorexia nervosa and 48 healthy-weight women. They measured the subjects’ blood levels of testosterone and free testosterone (the portion of testosterone that is active in the body). Both were lower in anorexic women than in the other subjects, even in normal-weight women who had amenorrhea—no menstrual periods—because of overexercise or stress.

The investigators also measured bone mineral density using densitometry (bone scans commonly called DEXA). Women with the lowest levels of free testosterone generally had the thinnest bones and the least muscle mass. Muscle mass also is important for maintaining healthy bones.

“This study identifies one possible cause of bone loss in a group of young women with a high prevalence of severely reduced bone density and increased fracture risk,” Miller said.

Free testosterone levels were reduced the most in women receiving oral contraceptives. This finding has been shown in healthy women but not previously in women with anorexia nervosa, Miller said. Anorexic women commonly are prescribed the pill, she explained, because they lose so much weight that they stop menstruating.

“Oral contraceptive therapy brings back their periods, but lower testosterone is an unintended consequence and may be bad for your muscles and bones,” Miller said. “We should ask: Are oral contraceptives good for women with anorexia nervosa?”

The study was funded by the National Institutes of Health. It was published in the Feb. 6 online issue of the Journal of Clinical Endocrinology and Metabolism, an Endocrine Society journal.

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