Effect of cholinergic muscarinic receptor blockade on human growth hormone (GH)-releasing hormone-(1-44)-induced GH secretion in acromegaly and type I diabetes mellitus.

In 10 patients with type I diabetes mellitus, 9 acromegalic patients, and 8 normal subjects, serum GH levels after an iv injection of 1 microgram/kg BW human GH-releasing hormone-(1-44) (GHRH) with and without cholinergic muscarinic receptor blockade (1 mg atropine, im, 15 min before GHRH) were measured. The GH increase after GHRH treatment in type I diabetic patients did not differ significantly from that in normal subjects. Pretreatment with atropine almost completely blocked the GH response to GHRH in patients with type I diabetes and normal subjects, but did not suppress the GH response to GHRH in acromegalic patients. These data indicate that cholinergic muscarinic receptors modulate GH secretion in normal man as well as in patients with type I diabetes mellitus, whereas acromegalic patients have a defect of cholinergic control of GH secretion.