Concordant and discordant adrenocorticotropin (ACTH) responses induced by growth hormone-releasing peptide-2 (GHRP-2), corticotropin-releasing hormone (CRH) and insulin-induced hypoglycemia in patients with hypothalamopituitary disorders: evidence for direct ACTH releasing activity of GHRP-2

Type 1 Diabetes Mellitus and Isolated Adrenocorticotropin Deficiency Manifested by Parkinsonism: A Case Report and Literature Review

“…GHRP-2 is a potent growth hormone secretagogue and has been shown to stimulate the secretion of ACTH and cortisol in humans (32). In addition, the stimulating effects of GHRP-2 on ACTH release have been suggested to be mediated via CRH and/or AVP, or may occur independently of both peptides (33,34). These findings suggest that, in the present case, administration of GHRP-2 may have stimulated corticotroph cells via pathways other than the CRH receptor under conditions of full endogenous CRH stimulation.…”

Investigation of the clinical significance of the growth hormone-releasing peptide-2 test for the diagnosis of secondary adrenal failure

“…The response of ACTH was previously found to be similar following GHRP-2 testing and ITT in patients with hypopituitarism, hence leading to the conclusion that the GHRP-2 test could be evaluated as an alternative to the ITT in assessing the HPA axis in patients with hypothalamic and/or pituitary disorders [15]. Alternatively, GHRP-2 was also reported to have a smaller effect on the hypothalamus as compared with the pituitary [17]. However, Kano et al reported an absence of a positive correlation between ACTH response to the GHRP-2 test and ITT, although they found a positive correlation between the cortisol response to the two tests in HPA axis failure [16].…”

“…Blood samples were collected before the injection and at 30, 60, 90, and 120 minutes after the injection. A peak ACTH level greater than 50 pg/mL or a rise two times higher than the basal level was the criterion for a normal response [17].…”

Is there an undiscovered neurocircuit for regulating GH secretion? -Pitfalls of GHRP-2 and ITT as GH provocative tests-

“…Meanwhile, most IGF-1 production in blood is mediated via GH, and the nocturnal secretion of GH is due to the neurocircuit of neurotransmitters in the central nervous system [11]. In patients with hypothalamus-pituitary disorders owing to disruption of pituitary stalk, GH secretion to GHRP-2 test was not responsive, but normal ACTH secretion to GHRP-2 test was reserved [30]. Consequently, the low GH and ACTH responses to GHRP-2 test was not explained by the disconnection between the hypothalamus and the pituitary gland.…”

“…The proposed mechanism by which ITT stimulates GH and ACTH, and AVP release is due to stimulation of GHRH and CRH and inhibition of SRIF release from the hypothalamus [2,6,7] and GHRP-2 may act on both the hypothalamus and the pituitary [9,22,[30][31]. In vivo, the GH-releasing activity of GHRP-2 increased BMI with a visceral obesity, although ITT test for GH secretion was not reexamined after one year later, because the ITT has a number of disadvantages, such as the potential for hypoglycemia-related adverse reactions which were sweating, palpitations and loss of consciousness as precoma shown in this subject [29].…”