Thyrotropin response to TRH stimulation in depressed patients with autoimmune thyroiditis

Two thyroid axis findings are often reported in depressed patients: autoimmune thyroiditis and abnormal thyrotropin (thyroid stimulating hormone, TSH) responses to thyrotropin-releasing hormone (TRH). The TSH response to TRH can be exaggerated, suggesting subclinical hypothyroidism; it can alternatively be blunted, for reasons poorly understood. We selected 28 women who had been found to have major depression for TRH testing. Fifteen patients had autoimmune thyroiditis and 13 had diffuse nontoxic goiter. The endocrinological diagnoses were verified by fine-needle aspiration biopsy and cytological assessment. Patients with overt hypothyroidism and hyperthyroidism were excluded from the study. There were no differences between the two groups in total triiodthyronine and thyroxine plasma levels or severity of depression. In the autoimmune group, basal TSH and Dmax TSH tended to be higher (p < 0.1); peak TSH was significantly higher (p < 0.05), suggesting that the prevalence of subclinical hypothyroidism was also higher. Blunted TSH responses were found about as often in one group as the other.