Adrenal adenomas: an overview

Adrenal adenomas are benign tumours of the adrenal cortex. Their incidence increases with age, reaching 10% in elderly individuals. They can be either functional (hormonally active) or non-functional. Non-functioning adenomas may not produce clinical symptoms or signs and can remain asymptomatic until discovered during imaging. Functional adrenal adenomas can produce excess glucocorticoids (resulting in Cushing's syndrome or mild autonomous cortisol secretion (MACS)), mineralocorticoids (resulting in hypertension and/or hypokalaemia) or androgens (usually symptomatic in female patients), although the latter is rare in isolation. Evaluation of an adrenal adenoma requires both imaging (non-contrast computed tomography is usually recommended, except in certain circumstances where magnetic resonance imaging might be more suitable) and hormonal work-up. Hormonal tests include a 1 mg overnight dexamethasone suppression test, plasma or urinary metanephrines and measurement of renin and aldosterone levels. If adrenocortical carcinoma is suspected, additional tests are needed which include measurement of sex hormones as well as steroid precursors. Adrenal adenomas are rare in childhood, and their incidence increases with age. The finding of adrenal adenoma in a child or young adult should raise the suspicion of malignancy. Small adenomas that are hormonally inactive can be followed up without immediate intervention. Adrenalectomy is the preferred treatment for hormonally active adenomas. This article reviews the evaluation and management of adrenal adenomas, including lesions found on routine imaging undertaken for other purposes (sometimes called adrenal ‘incidentalomas’).