Injections of the hormone leptin may be just what some women need to kick their reproductive system into action. A small study of 14 athletes who had stopped menstruating because of strenuous exercise and low weight showed that menstruation was restored in 5 of 8 of the women after twice-daily injections of leptin. The current study, reported in the New England Journal of Medicine (September 2, 2004), used Amgen Inc's version of leptin.

Because the researchers did not inject the other 6 volunteers with placebo shots, a more thorough 2-year test of 80 women is scheduled to begin to determine whether Amgen's leptin really works. Leptin has the potential to help women with anorexia nervosa, physically active women who have stopped menstruating, and women who are very thin and do not realize that they have a problem, according to Christos Mantzoros, MD, of Beth Israel Deaconess Medical Center in Boston, Mass.