Effect of 5-Hydroxytryptophan on Serum Cortisol Levels in Major Affective Disorders: III. Effect of Antidepressants and Lithium Carbonate

Serum cortisol levels were significantly increased following administration of 5-hydroxytryptophan (5-HTP), 200 mg orally, to patients with affective disorders. A three-to five-week period of treatment with lithium carbonate or monoamine oxidase (MAO) inhibitor augmented the mean 5-HTP-induced increase in serum cortisol concentration in manic or depressed patients, respectively: tricyclic antidepressant (TCA) and second-generation antidepressant treatment diminished the mean serum cortisol response in patients with major depression. These results are consistent with the hypothesis that lithium carbonate may enhance serotonin (5-HT) receptor sensitivity, whereas TCA and second-generation antidepressants diminish 5-HT receptor sensitivity. The enhancement of the cortisol response to 5-HTP by MAO inhibitors may be due to decreased metabolism of 5-HT. It is important to assess the effect of thymoleptic drug treatment on various responses to biogenic amine precursors or agonists in patients rather than laboratory animals.