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Exercise-induced amenorrhea, as well as shortened luteal phase and delayed menarche, have been attributed to a complex interplay of physical, hormonal, nutritional, psychological, and environmental factors that include stress of competition, decreased protein consumption, and altered lean-fat ratio (JAMA 1983; 249:354, JAMA 1981;246:1590, JAMA 1981;246:1559-1563, JAMA [MEDICAL NEWS] 1980;243:1699).
And although it is known that circulating levels of gonadotropins—necessary to induce ovulation—fall with exercise, the exact link between regular strenuous exercise and menstrual irregularities continues to puzzle investigators.
At the Seventh International Congress of Endocrinology in Quebec City, however, Lesley Rees, MD, who is chair of the British Society for Endocrinology, offered a new clue: Serum levels of β-endorphins increase with exercise, and these, in turn, appear to inhibit pituitary release of gonadotropins (luteinizing hormone, or LH, and follicle-stimulating hormone, or FSH).
β-Endorphins are a kind of endogenous opioid peptide, released from the anterior pituitary in response to stress (including
Ziporyn T. Latest clue to exercise-induced amenorrhea. JAMA. 1984;252(10):1258-1263. doi:10.1001/jama.1984.03350100002002