The effect of weight gain on gonadotrophins and prolactin in anorexia nervosa.
Serum levels of gonadotrophins and prolactin and their response to luteinizing hormone/follicle stimulating hormone--releasing hormone (LRH) and thyrotrophin releasing hormone (TRH) were measured in 14 females with anorexia nervosa when at low body weight and again in 6 cases during, and 12 cases after weight gain. Mean serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were low initially and whereas FSH increased significantly with weight gain, LH levels remained subnormal in most patients. LH responses to LRH were grossly impaired or absent in patients whose weight was below 75% of the ideal, but increased dramatically above this weight over-shadowing the more modest increase in FSH response. In three patients, however, impaired LH responses persisted as ideal weight was approached. Basal prolactin levels were well within the normal range in all patients. During weight gain there was no change in basal levels but the prolactin level 20 min after TRH was significantly increased.