Cushing's Syndrome

A "syndrome" refers to a set of symptoms which occur together and it can be caused by multiple etiologies. Cushing's syndrome is the result of hypersecretion of glucocorticoids. The four major causes are listed below. (Note that the first two causes are ACTH-dependent, related to excessive stimulation of the adrenals by ACTH).

a) Cushing's disease (pituitary-dependent bilateral adrenal hyperplasia). Many patients have a pituitary adenoma.

b) ACTH production in ectopic sites by some (non-pituitary) tumors, e.g. small cell carcinoma of lung, bronchial carcinoid, islet cell tumor, medullary thyroid carcinoma and others.

c) Autonomously functioning adrenal adenoma or adrenal carcinoma.

d) Administration of cortisol or other potent synthetic glucocorticoids (iatrogenic).

Cushing's syndrome is most commonly iatrogenic, resulting from chronic glucocorticoid therapy, Among the non-iatrogenic casues, Cushing's disease (due to pituitary adenoma ) is most frequent, accounting for 60-70% of the reported cases, ectopic ACTH secretion and primary adrenal tumor each accounts for 15-20%. Cushing's syndrome is rare in children. In contrast to the incidence in adults, adrenal carcinoma is the most frequent cause (50%) and adrenal adenomas are present in 14%. The major clinical features due to overproduction of glucocorticoids are central obesity ("buffalo hump" and "moonface"), diabetes mellitus, osteoporosis, hypertension, muscle wasting, increased growth of body hair in women, skin changes (skin atrophy and striae).

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