​Pathology - Cushing Syndrome
Cushing syndrome is caused by continuous exogenous glucocorticoid treatment, which is the most common cause of this illness. The term Cushing disease specifically refers to an ACTH-secreting pituitary adenoma, leading to an excess of endogenous cortisol secretion. Nonpituitary ACTH-secreting neoplasms or cortisol-secreting adrenal tumors also result in hypercortisolism. In addition to evaluating ACTH and cortisol levels, a dexamethasone suppression test is used to discriminate between pituitary and extra-pituitary sources: inability to suppress cortisol secretion with high doses of dexamethasone suggests an adrenal tumor. Regardless of causation, high cortisol causes muscle atrophy and leads to hyperglycemia owing to insulin antagonism. Hypertension and hypokalemia reflect stimulation of mineralocorticoid receptors, resulting to renal sodium retention and potassium squandering. Thinning of the skin, poor wound healing, redistribution of body fat, and psychological issues are pathologic outcomes of excess cortisol. Suppression of immunity raises the danger of infections. Treatment depends on the cause of hypercortisolism.
In this instance, moderate reduction in medication dose is necessary (rapid removal risks circulatory collapse due to a persistent condition of adrenal gland suppression from exogenous drug). Cases of pituitary or adrenal tumor are surgically treated.