Comparison of pituitary-adrenal responsiveness between insulin tolerance test and growth hormone-releasing peptide-2 test: a pilot study.
Insulin tolerance test (ITT) is the gold standard for assessing the hypothalamic-pituitary-adrenal (HPA) function. GH-releasing peptide (GHRP)-2, which has a strong GH-stimulating activity, is useful for diagnosing GH deficiency as well as ITT. Additionally, GHRP-2 is also known to activate HPA axis. There have been no comparative studies of pituitary-adrenal responsiveness between GHRP-2 test and ITT in patients with hypothalamic/pituitary disease. To assess whether GHRP-2 test could be an alternative to ITT for diagnosing HPA axis failure, both ITT and GHRP-2 test were performed in 15 patients suspected of hypopituitarism. A 100mug dose of GHRP-2 was administered intravenously and plasma ACTH and serum cortisol concentrations were measured. In ITT, a peak cortisol value over 18mug/dl is considered normal. Nine patients were diagnosed as HPA axis failure by ITT. Their median peak cortisol in GHRP-2 test was 11.4mug/ml. In 6 patients diagnosed as normal HPA axis status by ITT, their median peak cortisol in response to GHRP-2 test was 21.4mug/dl, significantly higher (p=0.0032) than seen in patients diagnosed as HPA axis failure. There was a strong correlation between the peak cortisol in GHRP-2 test and ITT (r=0.817; p<0.0001). When the cut-off value for the peak cortisol in GHRP-2 test was set to 13-14mug/dl for diagnosing HPA axis failure, the specificity and sensitivity were 100% and 88.9%, respectively. Although further studies that include normal subjects are needed, these preliminary results suggest the possibility that GHRP-2 test may be an alternative to ITT for assessing HPA axis function.
Kano
Toshiko
T
Department of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 1138603, Japan.
Sugihara
Hitoshi
H
Sudo
Mariko
M
Nagao
Mototsugu
M
Harada
Taro
T
Ishizaki
Akira
A
Nakajima
Yasushi
Y
Tanimura
Kyouko
K
Okajima
Fumitaka
F
Tamura
Hideki
H
Ishii
Shinya
S
Shibasaki
Tamotsu
T
Oikawa
Shinichi
S
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D001681:Biological Assay / Q000379:methods*; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007018:Hypopituitarism / Q000175:diagnosis / Q000503:physiopathology; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects* / Q000502:physiology; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides / Q000494:pharmacology*; D010865:Pilot Projects; D010913:Pituitary-Adrenal System / Q000187:drug effects* / Q000502:physiology
D007328:Insulin; D009842:Oligopeptides; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; C091874:growth hormone-releasing peptide-2; D006854:Hydrocortisone