Hormonal responses to fenfluramine in depressed and control subjects.

To investigate central neurotransmitter function in depression, baseline levels of serum cortisol and prolactin and the responses of these hormones to the putative serotonin agonist fenfluramine (60 mg, oral) were examined in 27 depressed patients and 14 normal subjects. Baseline cortisol was significantly elevated (P less than 0.01) in depressed subjects, whilst baseline prolactin was significantly reduced (P = 0.01) after covarying for cortisol. Although there were no significant abnormalities in either the prolactin or the cortisol response to fenfluramine in the total depressed group, the peak increase in prolactin levels (delta PRL) was significantly reduced (P less than 0.05) in subjects with endogenous depression. Analysis of covariance demonstrated, however, that the reduced delta PRL was partially dependent upon the abnormal baseline prolactin and cortisol levels. These results indicate the necessity of accounting for these baseline effects when investigating hormonal responses to the putative serotonergic challenges. The abnormal baseline findings are consistent with increased central noradrenergic activity in depression.