Effect of Clonidine on Growth Hormone, Prolactin, Luteinizing Hormone, Follicle-Stimulating Hormone, and Thyroid-Stimulating Hormone in the Serum of Normal Men

Clonidine (0.15 mg iv), a selective noradrenergic receptor agonist, increased serum growth hormone (GH) levels (greater than 6 ng/ml) on 8 out of 12 administrations to 6 normal men. This increase was independent of the hypotensive effects of the drug and unrelated to changes in serum cortisol. Clonidine induced a hyperglycemic effect in all subjects which was greatest 15 min after commencint the injection. No changes in blood sugar or GH occurred after placebo injection. Apomorphine, a selective dopamine receptor agonist, elevated GH in each of these 6 subjects (greater than 10 ng/ml). Clonidine had no effect on serum prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), or thyroid-stimulating hormone (TSH). These data are compatible with a dual dopaminergic and noradrenergic mechanism modulating GH secretion in normal men and with the absence of a noradrenergic mechanism in the regulation of PRL, LH, FSH, or TSH.