From the Guidelines
The best function screening tests for adrenal incidentalomas include a 1-mg overnight dexamethasone suppression test, plasma free metanephrines or 24-hour urinary fractionated metanephrines and catecholamines, and plasma aldosterone concentration to plasma renin activity ratio. These tests should be performed in all patients with adrenal incidentalomas to rule out functional tumors, even in the absence of clinical symptoms. For the dexamethasone suppression test, 1 mg of dexamethasone is taken orally at 11 PM, and serum cortisol is measured at 8 AM the next morning; cortisol levels >1.8 μg/dL suggest autonomous cortisol secretion, as recommended by the guidelines 1.
Key Screening Tests
- 1-mg overnight dexamethasone suppression test to screen for autonomous cortisol secretion
- Plasma free metanephrines or 24-hour urinary fractionated metanephrines and catecholamines to screen for pheochromocytoma, particularly in patients with adrenal incidentalomas that display ≥ 10 HU on non-contrast CT or who have signs/symptoms of catecholamine excess 1
- Plasma aldosterone concentration to plasma renin activity ratio to screen for primary aldosteronism in hypertensive patients
Rationale for Screening
These tests are essential because approximately 15-20% of adrenal incidentalomas are hormonally active, and identifying functional tumors guides appropriate management, as functional tumors typically require surgical removal while non-functioning tumors may be monitored conservically 1. The guidelines emphasize the importance of a multidisciplinary approach to the evaluation and management of adrenal incidentalomas, including the use of these screening tests to guide treatment decisions 1.
Clinical Considerations
For pheochromocytoma screening, plasma free metanephrines are preferred due to higher sensitivity, though 24-hour urine collection is an acceptable alternative. The aldosterone-to-renin ratio should be measured in hypertensive patients to screen for primary aldosteronism, with morning blood sampling after the patient has been upright for at least 2 hours. These considerations are crucial for ensuring that patients with adrenal incidentalomas receive appropriate care and management, as outlined in the guidelines 1.
From the Research
Function Screening Tests for Adrenal Incidentomas
The following are some of the best function screening tests for adrenal incidentalomas:
- 1-mg dexamethasone suppression test to rule out subclinical Cushing's syndrome 2, 3, 4
- Plasma metanephrines to evaluate for pheochromocytoma 3, 4
- Aldosterone/plasma renin activity measurements to evaluate for hyperaldosteronism, especially in patients with hypertension 3, 4
- Low-dose dexamethasone suppression test (LDDST) to evaluate for subtle glucocorticoid excess 5
- Basal dehydroepiandrosterone sulfate (DHEAS) measurement, which has been shown to be a sensitive and specific test for the detection of subclinical hypercortisolism in adrenal incidentalomas 4
- ACTH following overnight dexamethasone suppression, which can be used to verify autonomous cortisol secretion in patients with adrenal incidentalomas 6
Diagnostic Criteria
The diagnostic criteria for adrenal incidentalomas include:
- A detailed clinical history to rule out malignancy and functionality 2
- Radiographic assessment, including noncontrast and contrast computed tomography attenuation values expressed in Hounsfield units, to differentiate between benign and malignant adrenal masses 3
- Hormonal evaluation, including the tests mentioned above, to evaluate for subclinical Cushing's syndrome, pheochromocytoma, and hyperaldosteronism 2, 3, 4
Follow-up and Treatment
The follow-up and treatment of adrenal incidentalomas depend on the results of the initial evaluation:
- Patients with autonomous cortisol secretion may benefit from unilateral adrenalectomy, especially if they have comorbidities potentially related to hypercortisolism 2
- Patients with overt hormonal syndromes or suspected malignancy should undergo surgical excision of the adrenal mass 3
- Annual biochemical follow-up is recommended for most patients with adrenal incidentalomas, especially if the tumor is more than 3 cm in size, for up to 5 years 3