Plasma growth hormone and prolactin response to dopaminergic GABAmimetic and cholinergic stimulation in Huntington's disease.

We studied the acute effects of pharmacologic stimulation of neurotransmitter systems implicated in growth hormone and prolactin regulation in eight patients with Huntington's disease and matched control subjects. Both apomorphine, a dopamine agonist, and muscimol, a GABA agonist, produced an exaggerated rise in plasma growth hormone levels in the Huntington patients. Neither the growth hormone response to a muscarinic agonist, arecoline, nor the prolactin response to any of these drugs differed in the patients and controls. Loss of somatostatin activity in the hypothalamic-pituitary axis in Huntington's disease could account for these endocrinologic changes.