Do thyroid hormones mediate the effects of starvation on mood in adolescent girls with eating disorders?

In the eating disorders (ED) comorbid depression is common and clinical experience suggests that it is partly related to starvation. Starvation affects thyroid hormone status and thyroid hypofunction is in turn associated with depressed mood. We have therefore investigated the possibility that thyroid hormones and starvation are associated with mood in ED. Two-hundred and thirty-nine adolescent girls were examined at presentation of an ED. Analyses of thyroid hormones, documentation of weight and weight changes, self-reports of depressive symptomatology and clinical diagnoses of ED and depression were used in the analyses. Of the 239 girls 100 were diagnosed with depression. The girls with and without depression did not differ in age, weight, height, body mass index (BMI), weight loss or duration of disease. Plasma free thyroxine concentrations were lower in depressed girls (11.9±1.7 versus 12.8±1.9 pmol/L; p<0.01). Plasma triodothyronine and thyroid-stimulating hormone concentrations did not differ between groups. In a logistic regression analysis the odds ratio for depression was 41.1 (95% confidence interval 4.18-405; p=0.001) for a 10 pmol/L change of plasma free thyroxine after correction for BMI, weight loss, duration of disease, rate of weight loss, plasma triodothyronine and an interaction between BMI and plasma free thyroxine. BMI did not predict depression. Low circulating thyroxine concentrations may provide a link between starvation and depression in adolescent girls with ED.