PANCE Blueprint Endocrinology (6%)

Cushing’s syndrome

Patient will present with → buffalo hump, moon facies, pigmented striae, obesity, skin atrophy, hypertension, weight gain, hypokalemia

↑ cortisol, ↓ sodium, ↑ potassium, eosinophilia

Cushing syndrome is a constellation of clinical abnormalities caused by chronic high blood levels of cortisol or related corticosteroids

"Think of people with Cushing's Disease as "Cushy" - They have a buffalo hump, big puffy face and weight gain. Why weght gain? Cortisol stimulates fat and carbohydrate metabolism for fast energy, and stimulates insulin release and maintenance of blood sugar levels. The end result of these actions can be an increase in appetite"

Cushing's Disease: secondary - ↑ cortisol caused by a pituitary adenoma resulting in ↑ ACTH secretion.

Cushing's Syndrome: primary ↑ cortisol secretion from an adrenal tumor

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DEXAMETHASONE SUPPRESSION TEST AND 24 HOUR URINE CORTISOL

  • Gold standard test → Twenty-four-hour urine test: A test in which urine is collected for 24 hours to measure the amounts of cortisol. A higher than normal amount in the urine may be a sign of disease in the adrenal cortex
  • Low-dose dexamethasone suppression test: A test in which one or more small doses of dexamethasone are given. The level of cortisol is checked from a sample of blood or from urine that is collected for three days. This test is done to check if the adrenal gland is making too much cortisol.  In general, a clear failure to suppress cortisol levels in response to low-dose dexamethasone establishes the diagnosis.

Differentiating test for causes of Cushing's syndrome

  • High-dose dexamethasone suppression test (done in response to a positive low dose test): A test in which one or more high doses of dexamethasone are given. The level of cortisol is checked from a sample of blood or from urine that is collected for three days.
    • This test is done to check if the adrenal gland is making too much cortisol or if the pituitary gland is telling the adrenal glands to make too much cortisol
    • If cortisol production is suppressed then this is secondary to a pituitary ACTH secreting tumor
  • ACTH levels: Decreased ACTH = adrenal tumor, normal or increased ACTH means ectopic ACTH producing tumor

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Cushing's disease (pituitary/secondary) is treated with transsphenoidal surgery

Cushing syndrome (primary) ectopic or adrenal tumors: tumor is removed - Ketoconazole is given in inoperable patients

Iatrogenic steroid therapy - begin gradual steroid withdrawal to prevent Addisonian crisis

cushings syndrome

Secondary to increased levels of cortisol patients will develop a buffalo hump, moon facies, pigmented striae, obesity, skin atrophy, hypertension, weight gain, hypokalemia

Question 1
A 42-year-old woman comes to your office with the following signs and symptoms: obesity (she has gained 40 pounds in the past 6 months), elevated blood pressure at her last walk-in clinic visit, increased body hair, purple streaks on her abdomen, “a fat face” (her description), and pains in her bones and joints. She is taking no medication at present, nor has she been taking any medication for the past year. On examination, her body mass index is 35 kg/m2. Her blood pressure is 160/110 mm Hg; she has obvious hirsutism over her entire body, and her abdomen (which is obese) has purple striae. Her face not only is plethoric but also demonstrates a double chin. Her thoracic spine shows evidence of what is known as a buffalo hump. What is the most likely diagnosis?
A
Cushing's syndrome
B
Addison's syndrome
C
Prolactinoma
D
Hyperparathyroidism
Question 1 Explanation: 
This patient has Cushing's syndrome
Question 2
Of all the possible causes of the condition in this patient, which of the following is the most common?
A
adenoma of the adrenal gland
B
hyperplasia of the adrenal gland
C
carcinoma of the lung
D
corticosteroid therapy for suppression of inflammation
E
adenoma of the pituitary gland
Question 2 Explanation: 
The most common cause of Cushing syndrome is corticosteroid therapy. If steroids are excluded, the three major causes are as follows: (1) pituitary Cushing's disease (60% to 70%) as a result of an adenoma; (2) adrenal Cushing's disease (15%) from an adenoma, hyperplasia, or malignant neoplasm; and (3) ectopic Cushing's disease (15%) from a malignant neoplasm (small cell carcinoma of the lung). Thus, the most likely cause of Cushing syndrome in the patient described, who has not been taking any medication for more than 1 year, is a pituitary adenoma.
Question 3
Clinical findings associated with Cushing disease include all of the following, except
A
Weight gain
B
Menstrual irregularity
C
Depression/ emotional lability
D
Excessive thirst
E
Glucose intolerance
Question 3 Explanation: 
Cushing disease is defined as glucocorticoid excess due to excessive ACTH secretion from a pituitary tumor, the most common cause of primary Cushing syndrome. Cushing syndrome is defined as excessive corticosteroid exposure from exogenous sources (medications) or endogenous sources (pituitary, adrenal, pulmonary, etc. or tumor). Exogenous intake of steroids is the primary cause of secondary Cushing syndrome. In addition to the above common signs, physical findings include the following: • Obesity (usually central) • Facial plethora • Moon face (facial adiposity) • Thin skin • Hypertension • Hirsutism • Proximal muscle weakness • Purple striae on the skin • Acne • Easy bruisability
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