Clinical endocrinology
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Clinical endocrinology · Sep 2000
Dose-response relationship between plasma ACTH and serum cortisol in the insulin-hypoglycaemia test in 25 healthy subjects and 109 patients with pituitary disease.
The insulin hypoglycaemia test (IHT) is believed to be the most reliable test for evaluating the entire hypothalamo-pituitary-adrenal (HPA) axis. The lower limit for the normal peak serum cortisol response has been reported to be between 500 and 580 nmol/l. Reference levels for a normal plasma ACTH response have not been reported recently. ⋯ The normal increment of plasma ACTH in the IHT is greater than necessary for stimulating serum cortisol to levels > 500 nmol/l. Patients with a subnormal ACTH but normal cortisol response in the IHT have a decreased ACTH secretory reserve. It is unlikely that they are at increased risk of developing an adrenal crisis perioperatively or in other stressful situations unless pituitary function deteriorates. The ACTH-cortisol relationship in the IHT performed in patients with pituitary disease shows no sharp dividing line between normality and disease, and whether a patient needs permanent glucocorticoid substitution is a discretionary decision.