Serum thyrotropin (TSH) responses to thyrotropin-releasing hormone (TRH) in patients with anorexia nervosa and bulimia: influence of changes in body weight and eating disorders.

Serum thyrotropin (TSH) responses to thyrotropin-releasing hormone (TRH) were studied in 47 women with anorexia nervosa (AN) (group I) and in 11 bulimic patients of normal weight (group II). In group I, TSH responses were low in nine patients, delayed in 32 and normal in six. Patients with a normal TSH response had a lesser degree of anorexia than those with a delayed TSH response. Bulimia and vomiting were more frequently observed in the low response group. The maximum increase in TSH concentrations following TRH administration in the group I patients with vomiting (4.0 +/- 0.90 microU/ml, mean +/- S.E.) was significantly lower than that in the group I patients without vomiting or in normal controls (11.2 +/- 0.82 microU/ml and 11.1 +/- 2.34 microU/ml, respectively). Twenty-five patients with abnormal TSH responses in group I were retested after weight gain. Initially, TSH responses were low in six and delayed in 19. Following weight recovery, responses continued to be abnormal in five of the six and in eight of the 19, respectively. The symptoms of eating disorders continued in all patients with abnormal TSH responses even after weight recovery, whereas patients with normal responses after weight gain recovered from all symptoms. Of 11 patients in group II, six had abnormal TSH responses to TRH; the responses were delayed in four and low in two. Patients with normal responses had a lesser degree of eating disorder, compared with abnormal responders. These observations suggest that abnormal TSH responses in patients with AN were not necessarily due to weight loss alone; rather, they may be related to the eating disorder itself.