Subcutaneous glucagon as a test of the ability of the pituitary to secrete GH and ACTH.

Abstract

SUMMARYThe response to the subcutaneous injection of glucagon (1 mg) has been studied as a test of the ability of the pituitary to secrete ACTH and growth hormone (GH). Tests have been performed on fifteen normal subjects or patients with unrelated conditions, nine patients with pituitary tumours and seventeen with acromegaly. It is suggested that a normal response is a peak level of 5 ng/ml or more of GH (standard NIH GH 1216C) and either a rise of plasma cortisol measured by competitive protein binding of at least 4 μg/100 ml or a peak level of 7 μg/100 ml. In seventeen patients the responses were compared with those obtained in the insulin hypoglycaemia test and there was good agreement. Measurement of plasma ACTH showed that the response is at pituitary and not adrenal cortical level. Peak responses of ACTH and GH were obtrained at 150 min and of cortisol at 180 min. Plasma glucagon concentrations were falling steadily by this time although still above the control level. The mechanism of action of glucagon is not clear but does not appear to be related to fall of blood sugar. The subcutaneous injection of glucagon is not without side effects; about half the patients were nauseated and nine vomited. Nevertheless we believe that a subcutaneous glucagon test is of value for testing the pituitary reserve of ACTH and GH in situations where insulin hypoglycaemia cannot be used.