Adrenal incidentalomas and subclinical Cushing's syndrome: diagnosis and treatment

Adrenal incidentaloma has become a frequent clinical dilemma. Even in the absence of specific clinical features of Cushing's syndrome, adrenocortical incidentalomas may display steroid secretory activity at different degrees. The recognition of endocrine and metabolic dysfunctions associated with subclinical hypercortisolism leads to current awareness about its potential consequences.

Different protocols and threshold values to define normal cortisol secretion and diagnosis of subclinical Cushing's syndrome have been proposed, including recent practice guidelines for the diagnosis of overt Cushing's syndrome. Follow-up studies have provided additional data about the natural course of the disease and related cardiovascular and metabolic consequences. The study of bilateral adrenocorticotropin-independent macronodular adrenocortical hyperplasia in some familial cases offers a new approach to understanding the spectrum of subclinical cortisol hypersecretion.

The prevalence of subclinical hypercortisolism may be higher than previously reported as more sensitive diagnostic criteria are now recommended. The absence of a single gold standard test, the diversity of diagnostic criteria and the requirement of subsequent meticulous biochemical evaluations before a decision for treatment represent a challenge for the clinical management of this condition.