Long-term infusion of growth hormone release inhibiting hormone in acromegaly: effects on pituitary and pancreatic hormones.

Growth hormone release inhibiting hormone (GH-RIH) was infused at a rate of 1.3 mug/min for 28 hours into four patients with acromegaly, two of whom also had clinical diabetes mellitus. Growth hormone and glucagon were suppressed throughout the infusion though delayed secretion of insulin occurred in association with both meals and an oral glucose load. Glucose tolerance was improved in one diabetic patient who was taking chlorpropamide while the other required much less insulin than usual. Secretion of endogenous thyroid-stimulating hormone was lowered in one euthyroid patient on carbimazole. Luteinizing hormone, follicle-stimulating hormone, ACTH, and prolactin were not affected. Serum somatomedin levels were reduced in one patient. There was a rapid rebound of all the suppressed hormones when the infusions stopped. Longer-acting analogues of GH-RIH will be needed before long-term therapy of acromegaly or diabetes mellitus becomes possible, but such preparations should be available soon for clinical trial.