You Have an Adrenal Nodule Found by Accident: What the Evidence Says to Do Next

An adrenal mass found by accident on a scan ordered for something else needs two questions answered before anyone talks about surgery: does it look benign, and does it make excess hormone. The European Society of Endocrinology and European Network for the Study of Adrenal Tumors (ESE-ENSAT) guideline, published in 2023, answers the first with imaging density and the second with a short list of blood and urine tests. A homogeneous mass measuring 10 Hounsfield units or less on non-contrast CT is treated as a benign lipid-rich adenoma, and a normal 1-mg overnight dexamethasone suppression test rules out the most common hidden hormone problem. Most such nodules turn out to be harmless. This article explains the reasoning behind that workup, not a personal plan for any reader.

Why these masses get found at all

An adrenal incidentaloma is a mass one centimeter or larger discovered on imaging performed for an unrelated reason, such as a CT for abdominal pain or a stone. As cross-sectional imaging has become routine, these findings have become common, and the great majority are benign, non-functioning adenomas. That background matters, because it sets the goal of the workup: identify the small fraction that are either malignant or hormonally active, while sparing everyone else from anxiety, radiation, and unnecessary procedures.

The 2023 ESE-ENSAT guideline organizes the evaluation around exactly those two risks. Imaging addresses the question of cancer. Biochemical testing addresses the question of hormone excess. Both are done once at diagnosis for essentially every patient, and the results decide what, if anything, happens next.

What the CT density is actually telling you

The single most useful imaging number is the attenuation value on non-contrast CT, measured in Hounsfield units (HU). Adrenal adenomas, the most common benign tumor, are typically rich in intracellular fat, and fat is radiologically dark. A homogeneous mass with an attenuation of 10 HU or less is fat-rich enough to be called a benign adenoma with high confidence.

The 2023 guideline makes a notable move here. If a mass is homogeneous and 10 HU or less on non-contrast CT, it can be considered benign and needs no further imaging follow-up, regardless of size. That is a departure from older practice, which often imposed a size limit and scheduled repeat scans. The article by Park and Kim reviewing these updates frames this as one of the meaningful changes: density, not diameter, carries the benign call.

Masses that do not clear this bar get more scrutiny. Higher attenuation, heterogeneous texture, irregular margins, and larger size all raise concern. Lesions at or above 4 centimeters, or those with indeterminate imaging features, warrant multidisciplinary discussion because the probability of adrenocortical carcinoma rises with size. Additional imaging, such as delayed contrast washout studies or in some cases functional imaging, is reserved for masses that remain indeterminate after the first CT.

The hormone screen almost everyone gets

Even a benign-looking adenoma can quietly overproduce a hormone. The guideline recommends the same core screen for essentially all incidentalomas.

Cortisol

The first-line test is the 1-mg overnight dexamethasone suppression test (DST). The person takes 1 mg of dexamethasone late at night, and serum cortisol is measured the next morning. In a normally regulated adrenal, the dexamethasone signal suppresses cortisol. A morning cortisol of 50 nmol/L (1.8 micrograms per deciliter) or less is a normal, suppressed result and excludes autonomous cortisol secretion.

Catecholamines

To screen for a pheochromocytoma, a catecholamine-producing tumor, the guideline recommends measuring plasma free metanephrines or urinary fractionated metanephrines, particularly when imaging features are not clearly those of a benign adenoma.

Aldosterone

In patients who have hypertension or unexplained low potassium, the aldosterone-to-renin ratio screens for primary aldosteronism, a treatable cause of high blood pressure driven by aldosterone excess.

What mild autonomous cortisol secretion means

The most clinically interesting result is a dexamethasone test that does not fully suppress. When the post-dexamethasone cortisol is above 50 nmol/L (1.8 micrograms per deciliter) in a person who has no overt physical signs of Cushing syndrome, the guideline labels this mild autonomous cortisol secretion, or MACS. The name is precise: the gland is making cortisol somewhat independently of normal control, but not enough to produce the classic full syndrome.

A key simplification in the 2023 guideline is that MACS is now defined by that single threshold, without the older subdivisions that graded severity by how high the cortisol climbed. In practice, confirmation typically involves a repeat test rather than acting on one borderline value, and clinicians still weigh how far above the cutoff the number sits when deciding what to do.

Why does a mild finding get its own category? Because it is not biochemically silent. As Park and Kim summarize, MACS is associated with a higher prevalence of conditions such as type 2 diabetes and dyslipidemia, while progression to overt Cushing syndrome is rare, on the order of less than one percent. So MACS sits in an evidence gap: clearly linked to cardiometabolic burden, yet without randomized trials that settle whether removing the gland improves outcomes compared with monitoring.

How the pieces drive a decision

The guideline's logic is a decision tree, not a verdict. A homogeneous mass at 10 HU or less with a normal hormone screen is benign and non-functioning, and generally needs no imaging follow-up. A mass that is large, indeterminate on imaging, or clearly hormone-producing moves toward multidisciplinary review and, for many, surgery. MACS occupies the middle. For a person with a one-sided adenoma, a non-suppressing cortisol, and comorbidities plausibly linked to cortisol excess, the guideline supports discussing adrenalectomy, with the choice individualized to age, overall health, how persistently cortisol fails to suppress, the severity of those comorbidities, and personal preference.

That individualization is the honest reflection of the evidence. The imaging and biochemical thresholds are well defined and reproducible. The downstream management of the milder findings still depends on judgment applied to a specific person by their own clinicians.

This article is educational and is not medical advice. Anyone told they have an adrenal mass should have the imaging and hormone results interpreted by their own care team, who can place the numbers in the context of their history.