GROWTH-HORMONE RELEASING HEXAPEPTIDE-6 (GHRP-6) TEST IN THE DIAGNOSISOF GH-DEFICIENCY

Pituitary GH reserve can be assessed by substances that act directly a t the somatotroph, such as GHRH, or by a variety of metabolic and neur opharmacological tests acting at the hypothalamic level, such as hypog lycemia, clonidine or L-Dopa. In order to evaluate GHRP-6 as a test of pituitary GH reserve, we studied GH responses of i.v. administered GH RP-6 in a group of short-statured children, as well as in a group of a dults diagnosed with growth hormone deficiency (GHD) by conventional G H testing. Although we found that the GH response to GHRP-6 was lower in patients with GHD than in normal children, on an individual basis a considerable degree of overlap was observed between the two groups. I n contrast, we found an almost complete blockade of GH response to eit her GHRP-6 or GHRH plus GHRP-6 in patients with pituitary stalk transe ction, suggesting that this could be a cost-effective test for the dia gnosis of this condition, A similar finding was also obtained in GH re sponse to the combined administration of GHRH plus GHRP-6 in patients with GHD of adult onset; this test may well prove valuable in the diag nosis of this clinical entity.