Plasma gonadotrophins and LHRH infusions in anorexia nervosa

Nine female patients with anorexia nervosa were studied, three of them at different stages of weight gain. Basal plasma LH (luteinising hormone) was depressed in emaciated patients, but basal plasma FSH (follicle stimulating hormone) was normal. LH was significantly lower in patients who had been amenorrhoeic for less than 24 months than in those whose amenorrhoea was of longer duration. LH and FSH levels were stimulated by LHRH (luteinizing hormone releasing hormone), infused at a rate of 0.5 microgram/min for four hours. One patient, tested at 60% of standard weight, had no LH response. In all other patients below 70% of standard, the maximal LH response occurred within the first hour of infusion. In patients at higher weights, the LH response was biphasic, and the maximal level was reached during the last hour of the infusion. The FSH response, similarly, approached maximal during the first hour in patients below 70% of standard, but continued to rise throughout the infusion in patients at higher weights. Body weight expressed as a percentage of standard correlated significantly with both phases of the LH response, but not with the FSH response. Most previous authors have found an association between low body weight and depressed pituitary gonadotrophins in anorexia nervosa. The present findings further elucidate this relationship.