The clinical significance of adrenal incidentalomas

The term adrenal incidentaloma (AI) indicates an adrenal mass lesion > 1 cm in diameter discovered during testing for conditions unrelated to adrenal disease. The overall prevalence of these lesions ranges between 3% and 10%. Their incidence increases with age, and it is clinically important to identify AI associated with hormonal activity and/or malignant potential.

A detailed Medline search of all English language articles related to AI was carried out, and the clinical implications related to their hormonal activity and malignant potential are discussed.

The subclinical hypercortisolism observed in a significant percentage of patients with AI is associated with some of the detrimental effects of continuous autonomous cortisol secretion, including a higher prevalence of hypertension, dyslipidaemia, impaired glucose tolerance or type 2 diabetes mellitus and an increased risk for osteoporotic fractures. However, it remains to be proven whether treatment to reverse subtle glucocorticoid excess is beneficial. Clinically silent phaeochromocytomas and primary adrenal cancer are conditions associated with significantly high morbidity and mortality and require urgent treatment, while the prevalence and clinical significance of autonomous mineralocorticoid secretion are less clearly defined. Size and radiological features are the main predictors of malignant potential.

Patients harbouring AI should be evaluated for the possibility of malignancy and/or subclinical hypercortisolism which is associated with cardiovascular risk and bone loss. However, in the absence of prospective controlled studies correlating biochemical activity with end-organ complications, the long-term consequences of AI remain uncertain and their management remains largely pragmatic.