-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