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Insulin Tolerance Test

Meaning

The Insulin Tolerance Test (ITT) is a dynamic endocrine diagnostic procedure used to assess the functional integrity of the hypothalamic-pituitary-adrenal (HPA) axis and to quantify a patient’s sensitivity to insulin. The test involves administering a standardized dose of intravenous insulin to induce acute hypoglycemia, which is a powerful physiological stressor. The resulting counter-regulatory hormonal responses, specifically the secretion of cortisol and growth hormone, are then measured sequentially over time. This test is considered a gold standard for diagnosing secondary adrenal insufficiency and growth hormone deficiency, while also providing a direct measure of glucose disposal capacity.