The stimulation of growth hormone release by ACTH and its inhibition by somatostatin.

The rapid injection of 0.5 or 1.0 mg of tetracosacitid (Synacthen¿) was followed by a distinct increase of plasma growth hormone (GH) within 30 or 45 min in 5 of 7 normal volunteers. A second control test was performed in 3 of the 5 "responders" and 1 "non-responder" and showed a consistent reaction in all of them. The tests were then repeated in the 5 "responders" during an infusion of somatostatin (150 mug/h) and the GH response was totally abolished (3 subjects) or markedly reduced (2 subjects). Thus the ACTH induced GH release behaves in a manner similar to most other physiological or pharmacological stimuli of GH release. The cortisol output after ACTH was not altered by somatostatin.