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What is Which of the following is characteristic of Cushing's disease: and explain in detail?
Ref: Davidson 21st edition, pg 771Explanation:Cushing's syndrome refers to clinical features due to chronic exposure to excess of glucocorticoids of any etiology.Its of 2 types:ACTH- dependent Cushing's: Pituitary adenoma secreting ACTH (Cushing's disease), ectopic ACTH syndrome (Lung carcinoid, small cell ca lung, medullary ca thyroid, pheochromocytoma).ACTH- independent Cushing's: Iatrogenic (chronic glucocorticoid therapy), adrenal adenoma, adrenal carcinoma* Cushing's disease is due to a pituitary adenoma secreting ACTH.Pituitary microadenoma in 90%Cushing's syndrome is caused by excess activation of the GR (Glucocorticoid receptor)Anterior Pituitary--| |ACTH |(-)|Adrenal cortex | |Cortisol | |GR--Pseudo-Cushing's: Cortisol excess as a part of other illnessSeen in alcohol excess, chronic depression & primary obesityCarney's complex: cardiac myxomas, hyperlentiginosis, Sertoli cell tumor & PPAND (Primary Pigmented Nodular Adrenal Disease)McCune- Albright syndrome- Polyostotic fibrous dysplasia, precocious puberty & cafe- au-Iait spotsScreening tests: 24hr urinary free cortisol. Overnight dexamethasone test.--> Low dose dex testTreatment: Surgery for adrenal tumorsCushing's disease-removal of pituitary tumor via transsphenoidal approach; bilateral adrenalectomy for recurrenceOral agents for Cushings syndrome- metyrapone, ketoconazole, mitotaneIV etomidate in severe cases.