The diagnosis of adrenal insufficiency can be made by the finding of low morning serum cortisol concentration and low 24-hour urinary cortisol excretion, often with a subnormal response to corticotropin (ACTH). In some circumstances, however, other tests, such as insulin-induced hypoglycemia, are utilized to evaluate the response to stress, particularly when ACTH deficiency is suspected as the cause. This stress test also is used to establish a diagnosis of growth hormone deficiency. It has been used in patients with suspected Cushing's syndrome, but is not recommended as a diagnostic test in this setting.
Details of the insulin-induced hypoglycemia test in adults will be reviewed here. Additional information on the diagnoses of adrenal insufficiency, growth hormone deficiency, and Cushing’s syndrome in adults is reviewed separately. (See "Diagnosis of adrenal insufficiency in adults" and "Growth hormone deficiency in adults" and "Establishing the diagnosis of Cushing's syndrome".)
INSULIN-INDUCED HYPOGLYCEMIA TEST
Stress response — Stress is difficult to define, let alone to reproduce. However, hypoglycemia causes a major stress response, with increases in plasma corticotropin (ACTH) and serum cortisol, growth hormone, and prolactin, and activation of the sympathetic nervous system. (See "Physiologic response to hypoglycemia in normal subjects and patients with diabetes mellitus".)
Advantages/disadvantages — As a stress test, insulin-induced hypoglycemia has certain advantages:
●This test evaluates the integrity of the full hypothalamic-pituitary-adrenal axis as hypoglycemia acts centrally to stimulate hypothalamic corticotropin-releasing hormone (CRH) release and, therefore, ACTH release