Neuroendocrine effects of the dopamine agonist piribedil in depressed patients

Piribedil is a relatively selective dopamine agonist with moderate antidepressant activity. Although of limited clinical use, piribedil may elucidate the mechanism of the neuroendocrine effects of treatments useful in manic-depressive illness, particularly those involving the thyroid axis. Therefore, the effect of chronic piribedil treatment on peripheral thyroid hormones, as well as the pituitary hormone responses to sequential stimuli, namely arginine, thyrotropin-releasing hormone (TRH), and luteinizing hormone releasing hormone, were studied in patients with major depression. The drug was found to decrease peripheral thyroid hormones and the thyroid stimulating hormone response to TRH, but it did not affect prolactin, growth hormone, or the gonadotropins. The advantages of the experimental design and the implication of these findings for dopaminergic mechanisms in both the regulation of pituitary hormones and the treatment response of affective illness are discussed.