Thyroid function in bulimia nervosa.

Basal thyroid-stimulating hormone (TSH) and thyroid hormone levels were evaluated in 18 women with bulimia nervosa during a period of active binging and vomiting and again after 7 weeks of abstinence from these behaviors and compared to measures in 27 control women. In 10 of the patients and 11 of the controls, the TSH nocturnal surge was calculated from hourly TSH measurements obtained in the afternoon from 1500 to 1900 h and in the night from 2300 to 0400 h. During the binging phase of the illness patients had lower total triiodothyronine (T3) values than controls (p < .001). After 7 weeks without binge eating or purging, patients had lower T3, total thyroxine (T4), free triiodothyronine, free thyroxine (FT4), reverse triiodothyronine and thyroid-binding globulin (TBG) values compared to controls (p < .01) and significant reductions in T3, T4, FT4 and TBG compared to themselves in the active phase of the illness (p < .02). The reduction in thyroid hormone levels was not due to a reduction in the nocturnal thyrotropin surge, since surge values did not differ between normals and patients at either phase of the illness. Bulimics in the binging phase of the illness showed a positive correlation between caloric intake and TSH values (p < .01), suggesting that food binging may stimulate thyroid activity. In sum, these results show a substantial reduction in thyroid hormone levels after 7 weeks of abstinence from binging and vomiting behaviors.