-IBIS-1.5.0-
tx
endocrine system
Cushing's syndrome
diagnoses

definition and etiology

definition: Cushing's syndrome is a constellation of clinical abnormalities due to chronic exposure to excesses of cortisol (the major adrenocorticoid) or related corticosteroids; may be dependent or independent of ACTH regulation by the pituitary; "Cushing's disease" is generally accepted as referring to Cushing's syndrome from excess ACTH secretion

etiology: a pituitary adenoma may secrete excess ACTH; so may a nonpituitary tumor such as an oat cell carcinoma of the lung; it is often impossible to discern histologic abnormalities in the pituitary from which the overstimulation of the adrenal cortex arises. This suggests overstimulation of the pituitary by the hypothalamus.

signs and symptoms

Overproduction of cortisol causes the body to make sugar from its own tissues; this causes wasting of structural proteins, and increased blood sugar levels force the insulin response of fat production. From this arise a series of signs and symptoms:
• round "moon" facies
• truncal obesity with supraclavicular and dorsal cervical fat pads: "buffalo hump"
• distal extremities and fingers usually quite slender
• muscle wasting and weakness
• thin, atrophic skin with poor wound healing and easy bruising
• purple striae (stripes) may appear on the abdomen due to rapid growth of fat and weakened capillaries
• hypertension, renal calculi, osteoporosis, glucose intolerance are seen
• females often have menstrual irregularities
• increased production of androgens in addition to cortisol may lead to signs of virilism in females
Diagnosis is generally made via plasma cortisol measurements which should fall as the day goes on; a dexamethasone test is a good screening test.

lab findings:
• excess serum cortisol production with loss of diurnal variation
• increased urinary free cortisol (best test)
• increased urinary 17-KS, 17-OHKS
• dexamethasone depression test if any of above abnormal
• ACTH levels low or undetectable

course and prognosis

Once adrenal hyperfunction is established, radiographic studies of the pituitary should be ordered along with a careful search for nonpituitary ACTH-producing neoplasm; adrenal tumor should also be investigated.

Treatment involves controlling hyperfunction of the pituitary or adrenal cortex.

differential diagnosis

• pituitary adenoma
• ectopic ACTH-producing adenoma (primarily lung tumor)
• adrenal adenoma


footnotes