It is well known that the activation of the hypothalamus-pituitary-adrenal axis (HPA) by insulin-induced hypoglycemia (IIH) is more potent and multifactorial than that caused by CRH administration. In this study we compared the clinical value of both tests in assessing the integrity of the HPA system. Plasma ACTH and Cortisol responses to oCRH (1 μg/kg iv) and IIH (insulin 0.1 U/kg iv, glycemia <40 mg/dl) were compared in 15 patients with idiopathic GH deficiency. The CRH-induced mean ACTH response was lower, but not significantly, in patients than in controls (peak: 8.8 ± 1.7 vs 13.4 ± 2.2 pmol/l), while the mean Cortisol response was significantly lower than in normals (peak: 585.7 ± 49.5 vs 764.5 ± 52.2 nmol/l, p <0.005). Plasma ACTH and Cortisol responses to IIH were significantly lower than in normal subjects (peak: 22.3 ± 5.3 vs 35.8 ± 5.2 pmol/l, p<0.05 and peak: 566.5 ± 55 vs 803 ± 38.5 nmol/l, p <0.02, respectively). Both in controls and in patients the CRH-induced mean ACTH response was significantly lower (p <0.02) than that after insulin, while Cortisol peaks were not different. In conclusion, in patients with GH deficiency the impairment of ACTH secretion is not evident in basal condition, but it is disclosed after appropriate dynamic tests. It is confirmed that insulin hypoglycemia is a more potent stimulus than CRH for ACTH release.
- GH deficiency
- insulin hypoglycemia
- pituitary-adrenal axis
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism