Thyroid function in primary depression.

The thyroid function of 20 female inpatients with primary depression was investigated by the following tests: serum thyroxine, in vitro radioactive triiodothyronine uptake, free-thyroxine index, thyroidal 131I uptake and 48 hours protein-bound 131I. The mean values of serum thyroxine, free-thyroxine index and thyroidal 131I uptake of the patients were found decreased, compared to those of the euthyroid controls (to a statistically significant level for serum thyroxine and free-thyroxine index P less than .001). These findings point to a decreased thyroid activity in primary depression. The possibility of implication of a common neurochemical mechanism in both primary depression and thyroid hypoactivity was discussed.