Hypothalamic-pituitary-thyroidal axis alterations in bulimic patients

The hypothalamic-pituitary-thyroidal axis was studied in 17 normal-weight patients with bulimia. Basal levels of serum thyroxine (T4), triiodothyronine (T3), reverse triiodothyronine (rT3), and thyrotropin (TSH) were determined in all patients; responses of TSH and T3 to thyrotropin-releasing hormone (TRH) were investigated in nine patients. Mean basal serum T4, T3, and TSH concentrations were significantly lower in the patients than in the normal control subjects but serum rT3 levels were essentially the same. In nine patients TSH responses to TRH were normal in five, delayed in three, and low in one. The maximum increase in serum TSH and TSH net secretory response were not significantly different from those of control subjects. With respect to the T3 response to TRH, various indices in patients appeared significantly lower than in the control subjects. These results suggest that normal-weight patients with bulimia have abnormalities in the hypothalamic-pituitary-thyroidal axis.