Suppressive effect of cyproheptadine on L-DOPA-induced growth hormone release in man

In order to elucidate the relationship between dopaminergic and serotoninergic mechanisms in regulating secretion of human growth hormone (hGH), the effect of cyproheptadine, an antiserotoninergic agent, on l-DOPA-induced hGH secretion was studied in normal subjects. Oral administration of 500 mg of l-DOPA caused a rise in plasma hGH in 6 of 7 subjects studied. This rise in plasma hGH was significantly blunted by the intravenous infusion of 5 mg of cyproheptadine. These results suggest the close relationship between dopamine and serotonin in the control of hGH secretion.