From the Guidelines
To check for a functioning adenoma, a 1 mg dexamethasone suppression test is the preferred screening test for identifying autonomous cortisol secretion when clinically appropriate, as recommended by the most recent guideline 1.
Functioning Adenoma Diagnosis
The diagnosis of a functioning adenoma involves a combination of clinical evaluation, biochemical testing, and imaging studies.
- The initial work-up for an adrenal incidentaloma should include a focused history and physical examination aimed at identifying signs/symptoms of adrenal hormone excess, adrenal malignancy, and/or extra-adrenal malignancy 1.
- For suspected Cushing's syndrome from a cortisol-producing adenoma, a 1 mg dexamethasone suppression test is recommended 1.
- For patients with adrenal incidentalomas and hypertension and/or hypokalemia, screening for primary aldosteronism with an aldosterone-to-renin ratio is recommended 1.
- For suspected pheochromocytoma, plasma or 24-hour urinary metanephrines and catecholamines should be measured 1.
Imaging Studies
Imaging studies like non-contrast CT, washout CT, or chemical-shift MRI are typically performed to locate the adenoma and distinguish benign lesions from those that require further radiologic investigation 1.
- Non-contrast CT is a relatively inexpensive yet highly specific test for differentiating adenomas and some benign nonadenomas from malignant lesions 1.
- Delayed enhanced CT can also be used to distinguish adenomas and metastases, with adenomas tend to wash out faster after intravenous contrast 1.
Biochemical Testing
Biochemical testing is essential to demonstrate the hormonal abnormality caused by the functioning adenoma.
- For cortisol-producing adenomas, a 1 mg dexamethasone suppression test is the preferred screening test 1.
- For aldosterone-producing adenomas, plasma aldosterone-to-renin ratio testing is recommended 1.
- For suspected pheochromocytoma, plasma or 24-hour urinary metanephrines and catecholamines should be measured 1.
From the Research
Functioning Adenoma Tests
To check for functioning adenomas, several tests can be used, including:
- Measurement of a late-night salivary cortisol level, which is the best screening test for adrenocorticotropic hormone (ACTH)-secreting tumors 2
- Insulin-like growth factor 1 (IGF-1) levels and growth hormone levels to diagnose growth hormone-secreting tumors 2
- Prolactin levels to diagnose prolactinomas 2, 3
- Thyroid-stimulating hormone (TSH) levels to diagnose TSH-secreting tumors 2
Diagnostic Evaluation
All patients with pituitary tumors require endocrine evaluation for hormone hypersecretion 3 Patients with macroadenomas additionally require evaluation for hypopituitarism, and patients with tumors compressing the optic chiasm should be referred to an ophthalmologist for formal visual field testing 3
Imaging Tests
Imaging tests such as computed tomography (CT) and magnetic resonance imaging (MRI) can be used to evaluate adrenal tumors 4, 5 CT-guided biopsy can be considered to rule out metastatic disease in patients with active extraadrenal malignancy and a single adrenal lesion without suspicion for metastasis elsewhere 4
Rare Cases
In rare cases, plurihormonal pituitary adenomas can secrete multiple hormones, making diagnosis and management challenging 6 These cases require careful evaluation and management, and may involve a combination of surgical and medical therapies 6