Decreased thyroidal triiodothyronine secretion in patients with anorexia nervosa: influence of weight recovery.

Basal thyroxin (T4), triiodothyronine (T3), and thyrotropin (TSH) concentrations were significantly lower before weight recovery in 10 patients with anorexia nervosa (AN) than they were in control subjects. After weight recovery, basal T4 and TSH levels were unchanged and significantly lower in AN patients than in control subjects. Basal T3 concentrations increased significantly after weight gain: however, concentrations remained lower than those in the control subjects. The maximum increase in T3 and T3 net secretory response to thyrotropin-releasing hormone (TRH), obtained before and after weight recovery, appeared significantly lower than that in control subjects: however, the increases in TSH responses were not different from those of control subjects. Thus, low T3 concentrations in AN patients may be due not only to impaired peripheral conversion of T4 to T3 associated with the altered nutritional state, but also to decreased thyroidal T3 secretion in response to endogenous TSH, which is indicative of hypothalamic-pituitary-thyroidal dysfunction.