Discrimination between growth hormone (GH) deficiency of hypothalamic or pituitary origin: an aid in selecting patients for GH-releasing hormone (RH) prolonged therapy.

Eleven patients with GH deficiency (GHD) underwent i.v. GH-RH tests (1 mu/kg); 7 had idiopathic GH deficiency (IGHD) and 4 had multiple pituitary hormone deficiencies (MPHD)--diagnosed on the basis of the insulin hypoglycemia, clonidine and sleep tests. One test was done before and the other after five s.c. injections of 1 microgram/kg GH-RH given in the evening. There were three types of response: four patients in whom there was an increase of human GH (hGH) to twice the former level, from 11.6 +/- 4.9 to 22.8 +/- 7.3 ng/ml following priming (a partial hypothalamic lesion); five patients in whom there was no response to the pharmacological tests but the same rise of approximately 13 ng/ml in hGH in response in both acute GH-RH tests (partial pituitary lesion); and two patients with no response to the pharmacological and acute GH-RH tests (pituitary lesion). In all except one patient there was no change in the serum IGF-I values after 5 days priming with GH-RH. It is suggested that patients with a partial GHD due to a hypothalamic lesion might benefit from long-term therapy with GH-RH.