Lack of effect of hyperglycaemia on apomorphine induced growth hormone release in normal man

Six healthy adult males were studied to evaluate the effect of apomorphine on growth hormone (GH) secretion under normoglycaemic and hyperglycaemic conditions. Both under normoglycaemia and hyperglycaemia all subjects responded to the subcutaneous injection of 0.75 mg apomorphine hydrochloride with a marked increase in plasma GH concentration reaching a maximum after 30-60 min. In control studies no significant changes in plasma GH were observed following the injection of physiological saline. As apomorphine is considered a selective dopamine receptor stimulating agent, the results support the view that GH release in man can be modulated through a dopaminergic mechanism. The finding that the plasma GH rise after the administration of apomorphine is not suppressible by glucose indicates that apomorphine activates dopaminergic receptors localized distally in the hypothalamus or in the anterior pituitary. Amorphine in low dosage may be used clinically to test the capacity of the pituitary to release GH in man, at least in special cases.