Endocrine Abstracts

The characteristics of Cushing’s syndrome (CS) pathophysiology, the heterogeneity of its clinical presentation and the different patterns of ACTH and cortisol secretion independently of the cause make the diagnosis of ACTH-dependent CS a difficult task in some cases. Clinical symptoms are not always specific enough to establish the diagnosis. 1 mg DEX suppression is one of the most used tests for CS screening. Nocturnal salivary cortisol may be used, but its accuracy has to be validated in each laboratory and can be elevated in other diseases. Urinary free cortisol and nocturnal plasma cortisol are used to confirm the diagnosis. Stress, liver or renal disease, and interferences due to several drugs should be excluded. Severe mental disease and other clinical disturbances may also induce functional hypercortisolaemia, also called seudoCushing’s syndrome, confounding the real diagnosis. Differentiation of seudoCushing’s from mild ACTH-dependent CS is difficult. Combination DEX-CRH and, more recently, DDAVP stimulation, have been proposed, but these tests are not free of pitfalls. Episodic and cyclical disease can complicate the diagnosis, especially in quiescent secretory phases. To establish the origin of ACTH-dependent Cushing could represent a real challenge, since ACTH-secreting pituitary microadenomas can be small enough to be seen in MR studies, and, on the other hand, bronchial carcinoids may functionally behave as pituitary adenomas usually do. IPSS has to be considered before confirming an etiological diagnosis in those cases. PRL measurements can be useful to improve the performance of the procedure. Diagnosis of ACTH-independent CS is based upon consistent cortisol hypersecretion with low or undetectable ACTH levels. When patients present with bilateral or multiple adrenal masses associated to CS, a possible ACTH-independent macronodular hyperplasia with aberrant expression of adrenal receptors may be suspected. A correct diagnosis is essential for an effective therapeutic intervention.

Declaration of interest: The author declares that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.