Pituitary regulation of gonadal function was investigated in 39 consecutive men with treated and untreated coeliac disease and in an intestinal disease control group of 19 men with Crohn's disease of similar age and general nutritional status. Basal serum FSH concentration was increased in 10 of the coeliacs (26%) compared to only two of 19 men with Crohn's disease (11%). This abnormality was observed with equal frequency in both treated and untreated coeliacs, and was not associated with oligospermia. Serum LH concentration was increased in eight of 15 untreated coeliacs (53%) with sub-total villous atrophy, an abnormality which unlike the elevation of serum FSH, appears to return towards normal after gluten withdrawal. Serum LH was high in coeliacs despite marked elevation of the free testosterone index. Exaggerated responses of FSH and LH to LHRH were found in 89% and 45% respectively, of coeliacs with sub-total villous atrophy. However, exaggerated responses of LH alone were found more frequently in coeliacs than in men with Crohn's disease (P less than 0.02) and unlike the exaggerated FSH responses, LH responses were closely related to jejunal morphology. Exaggerated responses of FSH and LH in coeliacs were commonly found when basal gonadotrophin concentrations were normal. The occurrence of exaggerated gonadotrophin responses could not be related to plasma concentration of testosterone, dihydrotestosterone, oestradiol or the free testosterone index. Serum prolactin was modestly raised in 25% of untreated and partially treated coeliacs and in the same proportion of men with Crohn's disease. Elevated serum prolactin concentrations never exceeded 809 mU/l and were not associated with impotence or infertility. This study provides further evidence that in men with coeliac disease there is a derangement of pituitary regulation of gonadal function. This would seem to be part of a wider disturbance of central regulatory mechanisms of endocrine function in coeliac disease.