The secretion of luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyrotrophin (TSH) and prolactin (PRL, was studied in 17 women suffering from anorexia nervosa. The mean basal serum LH was reduced (8.4 ± 0.8 se mIU/ml; P < 0.001 vs normal controls), while LH increase after gonadotrophin-releasing hormone (LH-RH) appeared to be normal in 9 cases and impaired in 6 cases. The mean basal FSH did not significantly differ from normal subjects (3.9 ± 0.5 mIU/ml), while LH-RH administration elicited an exaggerated increase in 7 cases and a normal increase in 8 cases: the mean FSH response was significantly higher than in controls (P < 0.02). Plasma oestradiol-17β was reduced (20.4 ± 0.4 pg/ml; P < 0.001) while the serum testosterone levels were normal (0.73 ± 0.09 ng/ml). Clomiphene administration induced an increase in gonadotrophins in only 1 out of 7 patients. The mean serum TSH concentration was normal (2.3 ± 0.4 μU/ml), while serum thyroxine and triiodothyronine and free thyroxine index, though generally in the normal range, were significantly lower than values obtained in a control group (6.1 ± 0.4 μg/100 ml, P< 0.005; 102.3±7.7 ng/100 ml, P <0.005; 3.8±0.3, P < 0.05). Though the mean serum TSH increase after thyrotrophin-releasing hormone (TRH) was normal (12.0 ± 2.3 μU/ml), there were 4 impaired and 1 exaggerated increases, and 8 patients showed a delayed and frequently prolonged response. The increase in serum T3 after TRH appeared lower than in normal subjects (36.3 ± 1.8 ng/100 ml, P < 0.001). Serum PRL levels in basal conditions were higher than in the controls (19.4 ± 4.1 ng/ml, P < 0.001) while the increase in PRL after TRH was exaggerated in only 2 patients. The present data suggest that the primary failure in gonadotrophin secretion in anorexia nervosa occurs at hypothalamic level; moreover the data on TSH and PRL secretion also point to the existence of a hypothalamic disorder in this disease.

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