Criteria for subclinical Cushing’s syndrome:
(1) presence of an adrenal adenoma found incidentally (incidentaloma)
(2) no suspicion of adrenal disease prior detection of adrenal adenoma
(3) absence of a clear Cushingoid phenotype (although the patient may have facial roundness)
(4) autonomous cortisol secretion (ACTH-independent)
The patient may have:
(1) one ore more features of the metabolic syndrome
(2) osteoporosis
(3) a low serum ACTH
(4) urinary free cortisol concentration may be normal
Autonomous cortisol secretion is usually defined as an elevated serum cortisol after 1 mg overnight dexamethasone suppression test.
(1) Inadequate suppression is defined as a serum cortisol > 5 µg/dL (> 138 nmol/L).
(2) Adequate suppression (with subclinical Cushing syndrome excluded) is a serum cortisol < 50 nmol/L.(1.8 µg/dL).
(3) Serum cortisol levels between 50 and 138 nmol/L are indeterminate.
The diagnosis of subclinical Cushing’s syndrome should be suspected in a patient with indeterminate dexamethasone suppression if there are clinical features present (osteoporotic fractures, metabolic syndrome, etc).
