ROLE OF THE NEW GROWTH HORMONE-RELEASING SECRETAGOGUES IN THE DIAGNOSIS OF SOME HYPOTHALAMOPITUITARY PATHOLOGIES

Growth hormone (GH)-releasing hormone (GHRH) and somatostatin have a d ominant role in regulating GH secretion. However, results of studies u sing the new class of GH secretogogues, particularly GHRP-6, indicate that there may also be other, as yet undefined, hypothalamic mechanism s involved. Studies in adults with hypothalamopituitary disconnection (functional pituitary stalk transection), show GHRP-6-mediated GH rele ase to be completely blocked, indicating a main action at the hypothal amic rather than the pituitary level. The synergistic effect of GHRH p lus GHRP-6 administration on GH release seen in normal adults (and vir tually unaffected by age, obesity, or sex) is also absent in these pat ients, providing further support for this conclusion. Studies of the e ffects of GHRP-6 in children with GH deficiency due to perinatal pitui tary stalk transection have produced similar findings. It is suggested that the combined GHRH plus GHRP-6 test should be a promising tool fo r diagnosing GH deficiency states in both children and adults, and may identify a subgroup of patients with GH deficiency caused by interrup tion of the hypothalamopituitary connection. Copyright (C) 1996 by W.B . Saunders Company