The effect of methyltestosterone on the growth hormone response to the dopamine receptor agonist, apomorphine

Abstract

1. 1. There is some evidence that androgens affect dopaminergic function in animals and man. We investigated the effect of methyltestosterone (MT) (30 mg po) on the growth hormone (GH) response to the dopamine (DA) receptor agonist, apomorphine (Apo) HCl (0.5 mg sc), in 9 normal men. MT was given 2 hr before Apo. 2. 2. The peak plasma MT concentration was present 1 hr after administration (19.9±19.5 ng/ml: X ± SD): the concentration at 4 hr was 7.2 ± 4.9 ng/ml. At the time of Apo administration, plasma MT varied from 6.0–24.1 ng/ml. 3. 3. There was no significant effect of MT on Apo-GH secretion (interaction F(7, 56) = 1.08: p = NS). The mean individual peak GH concentration after Apo alone was 20.2 ± 11.9 (X ± SD) vs 22.2 ± 9.9 ng/ml when MT preceded Apo (p = NS). 4. 4. These results suggest that exogenous androgens do not affect DA receptor function in males with normal androgenic function. Lack of effect due to an insufficient dose or duration of administration of MT cannot be excluded.