CUSHING SYNDROME

Cushing syndrome is caused by prolonged exposure to elevated levels of either endogenous glucocorticoids or exogenous glucocorticoids.

Etiologies include:

1)      Pituitary adenoma: classic Cushing’s disease (80%); ↑ ACTH.

2)      Adrenal hyperplasia/neoplasia: ↓ ACTH.

3)      Ectopic ACTH production e.g. oat cell carcinoma, small-cell lung carcinoma or carcinoid tumor. ↑ ACTH.

4)      Iatrogenic: most common etiology, chronic steroid use. ↓ ACTH.

Individuals with Cushing Syndrome can develop moon facies, facial plethora, supraclavicular fat pads, buffalo hump, truncal obesity, and purple striae. Often complain of proximal muscle weakness, easy bruising, weigh gain, hisutism, and, in children, growth retardation. Hypertension, osteopenia, diabetes mellitus, and impaired immune function may occur.

Exogenous steroids may cause suppression of the hypothalamus-pituitary-adrenal (HPA) axis, which can last for as long as a year after exogenous steroids administration has ended.

An individual with HPA axis suppression cannot increase steroids production appropriately during a medical illness or other stress, and would need to receive stress doses of steroids to avoid adrenal crisis. Thus, in an emergency, the potential for relative adrenal insufficiency should be considered in any patient with Cushing syndrome.

ADRENAL CRISIS

Adrenal crisis may occur in patients on steroids who stop taking their glucocorticoids or neglect to increase their steroid during an acute illness. It also may occur in patients who have recently undergone resection of an ACTH-producing or cortisol-producing tumor, or who are taking adrenal steroid inhibitors.

Finding: Hypotension, abdominal pain, vomiting, and mental confusion (secondary to low serum sodium or hypotension), hypoglycemia, hyperkalemia, hyponatremia, and metabolic acidosis.

Biochemical evaluation of Cushing syndrome.

Four methods are accepted for the diagnosis:

1)      Urinary free cortisol levels.

2)      Low-doses dexamethasone suppression test.

3)      Evening serum and salivary cortisol levels.

4)      Dexamethasone-corticopropin-releasing hormone test.

Treatment:

The Cushing syndrome treatment is directed by the primary cause of the syndrome.

A culprit tumor should be removed if possible.

For exogenous etiology a gradual withdrawal of glucocorticoids is the way.