Protirelin stimulation test and thyroid function during treatment of depression.

Thyroid levels were estimated in 15 patients with endogenous depressions. Before electroconvulsive treatment (ECT), serum thyroxine (T4) and free T4 index values were elevated (P less than .02). After recovery from depression, the levels were normal. Serum triiodothyronine (T3) and free T3 index were normal both before and after ECT. Serum thyrotropin (TSH) levels were also normal and not substantially altered by the ECT procedure. The mean maximal TSH response to protirelin (thyrotropin-releasing hormone) was diminished in the depressed patients and normal after recovery. In three patients, the increase in TSH response to protirelin after recovery did not occur and they relapsed within six months, while in seven patients with increased TSH response to protirelin after recovery only one relapse occurred. The disturbances in the free T4 index, T4, and the protirelin test may in some depressed patients resemble hyperthyroidism, but this condition can be excluded by means of serum, T3 and free T3 index.