Cushing syndrome

Cushing syndrome is the clinical manifestation of pathological hypercortisolism from any cause.

Exogenous corticosteroid exposure is the most common cause of Cushing syndrome. Cushing's disease, which is hypercortisolism caused by an adrenocorticotrophic hormone (ACTH)-secreting pituitary adenoma, is the most common cause of endogenous Cushing syndrome, and is responsible for 70% to 80% of cases.

It may be difficult to distinguish patients with mild Cushing syndrome from those with the metabolic syndrome (central obesity with insulin resistance, and hypertension). Features more specific to Cushing syndrome include proximal muscle weakness, supraclavicular fat pads, facial plethora, violaceous striae, easy bruising, and premature osteoporosis.

After excluding exogenous corticosteroid use, patients with suspected Cushing syndrome should be tested for hypercortisolism with one of three high-sensitivity tests (late-night salivary cortisol, 1 mg overnight low-dose dexamethasone suppression testing, or 24-hour urinary free cortisol).

At least one additional test should be performed to confirm hypercortisolism in patients with a positive initial screening test.

Once endogenous hypercortisolism is confirmed, plasma ACTH should be measured. If ACTH is suppressed, diagnostic testing should focus on the adrenal glands. If ACTH is not suppressed, pituitary or ectopic disease should be sought.

Surgical resection of the pituitary or adrenal adenoma that is causing hypercortisolism is the primary treatment of choice in the vast majority of patients with endogenous Cushing syndrome.

Cushing syndrome is the clinical manifestation of pathological hypercortisolism from any cause. Patients often display weight gain with central obesity, facial rounding and plethora, proximal muscle weakness, and thinning of the skin. They also develop metabolic complications including diabetes mellitus, dyslipidaemia, metabolic bone disease, and hypertension. Cushing syndrome can be caused by exogenous corticosteroid exposure, by adrenocorticotrophic hormone (ACTH)-secreting pituitary tumours (termed Cushing's disease), by autonomous adrenal cortisol overproduction, and, rarely, by ectopic ACTH-secreting tumours.[1]Lacroix A, Feelders RA, Stratakis CA, et al. Cushing's syndrome. Lancet. 2015 Aug 29;386(9996):913-27. http://www.ncbi.nlm.nih.gov/pubmed/26004339?tool=bestpractice.com