Dependency of tricyclic antidepressant efficacy on thyroid hormone potentiation: case studies

Two patients are described who depended on potentiation of tricyclic antidepressant effectiveness by thyroid superfunction for remission of an episode of unipolar depression. In one case, the excess thyroid hormone was the product of hyperthyroidism; whenever the hyperthyroidism was treated, the remission induced by imipramine was negated. In the other case, triiodothyronine was exogenously administered. These case studies suggested that some patients may require larger doses than 25 microgram of triiodothyronine per day for effective antidepressant potentiation. Some endocrinological similarities between hyperthyroidism and depressive illness are discussed.