Cushing syndrome

Question 1

What is Cushing’s syndrome?

Answer 1

Endocrine disorder that is most often caused iatrogenically by the exogenous administration of glucocorticoids

Question 2

What are the types of causes of Cushing’s syndrome?

Answer 2

(Exogenous) Hypercortisolism as a result of prolonged glucocorticoid therapy
(Endogenous, primary) Autonomous overproduction of cortisol by the adrenal gland leading to ACTH suppression (i.e. Adrenal adenomas, Adrenal carcinoma)
(Endogenous, secondary) Pituitary adenomas → ACTH secretion or Paraneoplastic syndrome → ACTH secretion (i.e. Small cell lung cancer, Renal cell carcinoma)

Question 3

What are the clinical features of Cushing syndrome?

Answer 3

(Skin) Thin, easily bruisable skin with stretch marks, Hirsutism, Acne
(Musculoskeletal) Osteoporosis, pathological fractures, Muscle atrophy/weakness
(Endocrine/Metabolic) Weight gain characterized by central obesity, moon facies, and a buffalo hump; insulin resistance

CUSHINGOID” is the acronym for side effects of corticosteroids: C = Cataracts, U = Ulcers, S = Striae/Skin thinning, H = Hypertension/Hirsutism/Hyperglycemia, I = Infections, N = Necrosis (of femoral head), G = Glucose elevation, O = Osteoporosis/Obesity, I = Immunosuppression, D = Depression/Diabetes

Question 4

What are the laborotroy findings in Cushing’s syndrome?

Answer 4

Hypernatremia, hypokalemia, metabolic alkalosis
Hyperglycemia
Hyperlipidemia

Question 5

How is Cushing’s syndrome and its cause diagnosed?

Answer 5

(Serum ACTH levels) Low (< 5 pg/mL): suspect primary hypercortisolism
High (> 20 pg/mL) suspect secondary hypercortisolism

If secondary dose suspected:
(High-dose dexamethasone suppression test) suppression of cortisol levels to less than 50% of baseline = Cushing’s disease
No suppression = ectopic ACTH production

(CRH stimulation test) ACTH and cortisol levels increase further = Cushing’s disease
No increase in ACTH or cortisol levels = ectopic ACTH production

Question 6

What is the treatment for Cushing’s syndrome?

Answer 6

(Exogenous) lowering the dose of glucocorticoids

(Endogenous) (Inoperable types) Drugs to suppress cortisol synthesis (i.e. metyrapone, mitotane, ketoconazole)
(Operable types) Resection of adenoma or tumour