Cortisol responsiveness to insulin-induced hypoglycemia in Cushing's syndrome with huge nodular adrenocortical hyperplasia.
A 51-yr-old male patient with a 3 yr history of Cushing's syndrome is described. The baseline plasma cortisol level was elevated, while the plasma ACTH levels remained at an undetectable level. Dynamic testing of pituitary-adrenal function revealed no suppression after 8 mg of dexamethasone, and there was no response to metyrapone or CRF, while plasma cortisol showed a hyperresponse to synthetic ACTH. Plasma cortisol responded to insulin-induced hypoglycemia without an obvious ACTH response. These and the computerized tomography data suggested a "huge" bilateral nodular adrenocortical hyperplasia which was later confirmed by surgery. The left and right adrenal glands weighed 55 and 76 g, respectively. In vitro experiments, using the adrenal tissue, showed that there was an adrenal cortisol response to 1-39 ACTH but not to regular insulin, arginine vasopressin, angiotensin II, norepinephrine or epinephrine. These results indicate that plasma cortisol responded to a slight hypoglycemia-induced plasma ACTH change which was not detected in the ACTH radioimmunoassay or to factors other than ACTH which might be induced by hypoglycemia.
D000302:Adrenal Cortex / Q000473:pathology*; D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D001127:Arginine Vasopressin / Q000494:pharmacology; D002940:Circadian Rhythm; D003480:Cushing Syndrome / Q000097:blood*; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D006965:Hyperplasia; D007003:Hypoglycemia / Q000097:blood*; D007328:Insulin; D008297:Male; D008797:Metyrapone; D008875:Middle Aged; D009638:Norepinephrine / Q000494:pharmacology; D010912:Pituitary-Adrenal Function Tests
D007328:Insulin; D000804:Angiotensin II; D001127:Arginine Vasopressin; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone; D009638:Norepinephrine; D004837:Epinephrine; D008797:Metyrapone