Low serum triiodothyronine in patients with anorexia nervosa.

Patients with anorexia nervosa can demonstrate clinical and/or laboratory findings suggestive of reduced thyroid hormone secretion. In this study, the thyroxine (T4) and triiodothyronine (T3) serum concentrations, and thyrotropin (TSH) response to intravenous administration of thyrotropin releasing hormone (TRH) were determined in 6 patients (aged 9 to 15 yr) with anorexia nervosa and the results compared to those found in a group of 15 normal subjects. The mean basal TSH concentration and mean maximum increase in TSH after TRH were comparable to those in the normal subjects. The mean T4 concentration (7.2 mug/100 ml) in the anorexia nerovsa group was slightly but significantly lower than in the normal group (9.5 mug/100 ml). Five of the 6 patients had serum T3 concentrations below the lower limits of normal and the mean T3 concentrations (49.7 ng/100 ml) was significantly lower than in the normal group (106 ng/100 ml). The extremely low serum levels of T3 in these patients with anorexia nervosa suggest that peripheral conversion of T4 to T3 is impaired during chronic starvation.