Endocrine Abstracts

Background: Pseudo-Cushing’s syndrome (PCS) constitutes a group of physiological or non-physiological medical conditions that mimic Cushing’s syndrome (CS) clinical features along with a mild biochemical hypercortisolaemia which remains under a physiological feedback hormonal control. Physiological conditions such as pregnancy, surgical or emotional stress, severe illness, intense chronic exercise, and non-physiological as chronic alcoholism, obesity, metabolic syndrome, poorly controlled diabetes mellitus, major depression, malnutrition, anorexia nervosa represent a PCS.

Aim of this presentation: The aim of this presentation is to unravel the diagnostic tools that are currently available to differentiate CS from PCS.

Methodology: Differential diagnosis is often challenging since we now frequently see mild cases of CS while symptoms and signs of CS may be present in PCS.

Results: Clinical examination is helpful when signs such as easy bruising without an obvious trauma, facial plethora, proximal myopathy, reddish purple striae (1 cm wide), unexplained osteoporosis or weight gain with decreasing growth in children, suggest hypercortisolism. Biochemical diagnosis in CS includes late-night salivary cortisol (LN-SC), dexamethasone suppression test (DSST), and urinary free cortisol (UFC) as screening tests. However, UFC may be elevated in severe obesity but not in mild or cyclic CS. Dexamethasone suppression-corticotropin-releasing hormone (CRH) test combining the low-dose DSST and the CRH test is based on the fact that dexamethasone suppresses serum cortisol levels in normal individuals as in a small number of those with Cushing’s disease (CD), but following CRH administration only patients with CD respond with an increase in ACTH and cortisol secretion. Moreover, desmopressin stimulation test is based on the fact that the vasopressin analogue desmopressin (1-deamino-8D-arginine vasopressin, DDAVP) stimulates ACTH release, representing an aberrant response of neoplastic cells in patients with CD but not in patients with PCS. Finally, LN-SC or midnight serum cortisol demonstrated high diagnostic accuracy in differentiating patients with PCS compared to patients with CS.

Conclusion: Since there is no biochemical suppression or stimulation test and no individual clinical feature that may warrant a 100% diagnostic accuracy for the discrimination of CS from PCS, their combination probably represents the most useful tool for the physicians to challenge this differential diagnosis.