Cushing's syndrome (adrenal)
ACTH dependent Cushing's syndrome is a secondary hyperfunction of the zona fasciculata in the adrenal cortex. This disease is mostly due to an ACTH-secreting pituitary adenoma or rarely due to ectopic ACTH production. The excess of ACTH (1) results in overproduction of glucocorticoids and to a much lesser extent of mineralocorticoids and androgens. Increased glucocorticoid levels result in the characteristic symptoms such as moon face, myopathy, obesity, buffalo hump, hypertension, and glucose intolerance.
ACTH independent Cushing's syndrome is caused by cortisol overproduction by the adrenal due to an adenoma or carcinoma. So, this disease state involves high cortisol levels, but impaired ACTH levels (negative feedback of cortisol). High glucocorticoid levels in the blood cause similar symptoms as discussed above. Drugs that inhibit glucocorticoid synthesis are used to treat this disease, in the period prior to final treatment by surgical removal of the tumors that cause Cushing's syndrome.
I. Treatment with exogenous steroids may induce Cushing’s syndrome.
II. ACTH independent Cushing’s syndrome can be caused by a tumor.