Melatonin and pituitary-gonadal function in disorders of eating behavior.

In order to study the possible relationships between melatonin secretion and pituitary-gonadal function, the circadian rhythm of plasma melatonin, the basal levels of estradiol-17beta and testosterone and the luteinizing hormone (LH) and follicle-stimulating hormone (FSH) response to luteinizing hormone-releasing hormone (LH-RH) stimulation were evaluated in normally cycling healthy women and in two groups of women with menstrual dysfunctions related to eating disorders (19 patients with anorexia nervosa and 16 with primary obesity). The circadian rhythm of plasma melatonin reached statistical significance in anorectic patients but not in obese patients. The mean 24 h melatonin level was significantly higher in anorectic than in obese patients and in control subjects.