The corticotropin-releasing hormone test in normal short children: comparison of plasma adrenocorticotropin and cortisol responses to human corticotropin-releasing hormone and insulin-induced hypoglycemia

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Abstract
The human corticotropin-releasing hormone (hCRH) tests were performed in twelve normal short children, and the responses of plasma ACTH and cortisol to iv administration of 1 μg/kg hCRH were compared with those to insulin-induced hypoglycemia. After administration of hCRH, the mean plasma ACTH level rose from a basal value of 3.3 ± 0.4 pmol/l (mean ± sem) to a peak value of 9.2 ± 0.8 pmol/l at 30 min, and the mean plasma cortisol level rose from a basal value of 231 ± 25 nmol/l to a peak value of 546 ± 30 nmol/l at 30 min. The ACTH response after insulin-induced hypoglycemia was greater than that after hCRH administration; the mean peak level (P < 0.01), the percent maximum increment (P < 0.01), and the area under the ACTH response curve (P < 0.01) were all significantly greater after insulin-induced hypoglycemia than those after hCRH administration. Although the mean peak cortisol level after insulin-induced hypoglycemia was about 1.3-fold higher than that after hCRH administration (P < 0.01), neither the percent maximum increment in plasma cortisol nor the area under the cortisol response curve after insulin-induced hypoglycemia was significantly different from that after hCRH administration. Consequently, the acute increases in plasma ACTH after the administration of 1 μg/kg hCRH stimulated the adrenal gland to almost the same cortisol response as that obtained with a much greater increase in plasma ACTH after insulin-induced hypoglycemia. These results suggest that a plasma ACTH peak of 9–11 pmol/l produces near maximum acute stimulation of adrenal steroidgenesis.