PLASMA GH RESPONSE TO THE SEQUENTIAL 3 DAY ADMINISTRATIONS OF GHRH FOLLOWED BY ARGININE INFUSION IN PATIENTS WITH IDIOPATHIC GH DEFICIENCY AND NORMAL SHORT CHILDREN

To study the site of lesions in idiopathic growth hormone (GH) deficie ncy (IGHD), growth hormone releasing hormone (GHRH) was administered s equentially for 3 days to 19 patients with IGHD, 3 patients with GH de ficiency (GHD) secondary to hypothalamic tumors, and 7 normal short ch ildren (NSC). GHRH (100 mug) was injected as a bolus on days 1 and 3, and was infused over 60 min on day 2. Of 19 patients with IGHD, 6 show ed an improved GH response (group A), 5 a decreased response (group B) and the remaining 8 an unchanged response (group C) to sequential adm inistration of GHRH. The response was unchanged in patients with secon dary GHD or NSC. There was no significant correlation between the patt erns of GH response and the findings on pituitary MR images or the del ivery state at birth in IGHD patients. Ten patients with IGHD (4 of gr oup A; 3 each of groups B & C) and 2 NSC showed much greater GH respon ses to arginine (0.5 g/kg i.v. for 30 min) injected with preceding GHR H than to arginine injected without preceding GHRH. These results indi cate that hypothalamic lesions were primarily responsible for GH defic iency in about 60% of the patients with IGHD (groups A and B), and gro up C might have more severe hypothalamo-pituitary damages than the oth er groups. Hypothalamic somatostatin neurons seems to be functioning t o a degree even in severe IGHD patients.