Psychiatric applications of thyroid tests.

Thyroid tests, especially the TRH test, can aid psychiatrists in the same way that laboratory tests are used in other medical specialties. Such tests augment clinical judgment and provide information about possible primary thyroid disturbances. The TRH test has the added value of prognostic significance when repeated after a course of treatment. Thyroid tests may also identify subgroups of depressed patients who can benefit from thyroid hormone replacement or who require T3 potentiation of tricyclics, as well as those patients with bipolar illness who are hypothyroid and may be at risk for rapid cycling.