What are the current clinical guidelines for diagnosing and treating adrenal (suprarenal) gland disorders, including Cushing's syndrome, primary adrenal insufficiency, pheochromocytoma, primary hyperaldosteronism, and adrenal incidentalomas?

Clinical Guidelines for Adrenal (Suprarenal) Gland Disorders

For adrenal gland disorders, implement a systematic three-pillar diagnostic approach: imaging characterization, comprehensive hormonal evaluation, and growth surveillance, with management decisions driven by malignancy risk and hormonal functionality. 1, 2

Diagnostic Framework

Initial Imaging Assessment

When an adrenal mass is detected, obtain unenhanced CT as the first-line imaging modality to assess Hounsfield units (HU) 2:

• HU ≤10: Benign lesions (0% malignancy risk) - no additional imaging needed regardless of size
• HU 10-20: Indeterminate (0.5% malignancy risk) - requires comprehensive evaluation
• HU >20: Suspicious (6.3% malignancy risk) - warrants multidisciplinary discussion and likely surgery if >4 cm and inhomogeneous 3, 2

Critical pitfall: Do not skip unenhanced CT measurements. Contrast-enhanced studies alone cannot reliably assess HU attenuation values.

Mandatory Hormonal Evaluation

Every patient with an adrenal mass requires screening for three conditions 2:

1. Autonomous cortisol secretion: 1-mg overnight dexamethasone suppression test (DST)

   • Take 1 mg dexamethasone at 23:00-24:00
   • Measure serum cortisol at 08:00-09:00 next morning
   • Cortisol ≤50 nmol/L (≤1.8 μg/dL): Normal, excludes cortisol excess
   • Cortisol >50 nmol/L (>1.8 μg/dL): Mild autonomous cortisol secretion (MACS)
   • Cortisol >138 nmol/L (>5 μg/dL): Definite autonomous cortisol secretion 1, 2

2. Pheochromocytoma: Plasma-free metanephrines or 24-hour urinary metanephrines 4, 2

3. Primary aldosteronism (if hypertensive or hypokalemic): Aldosterone-to-renin ratio

   • Ratio >30: Requires confirmatory testing 1

Measuring dexamethasone levels alongside cortisol improves DST interpretability 4

Condition-Specific Management

Cushing's Syndrome/Disease

For suspected Cushing's syndrome, start with either 24-hour urinary free cortisol (UFC) and/or late-night salivary cortisol (LNSC); DST is an alternative if LNSC is not feasible 4:

• UFC: Average 2-3 collections
• LNSC: ≥2 tests on consecutive days
• DST: Useful in shift workers; avoid in women on estrogen-containing oral contraceptives

If adrenal tumor-related Cushing's is suspected, start with DST as LNSC has lower specificity in these patients 4

Confirming Cushing's Disease (Pituitary Source)

After confirming hypercortisolism, measure ACTH 4:

• Low ACTH: ACTH-independent (adrenal source) → Proceed to adrenal CT/MRI
• Normal/high ACTH: ACTH-dependent → Obtain pituitary MRI

For pituitary lesions 4:

• ≥10 mm adenoma: Presumed Cushing's disease, no IPSS needed
• <6 mm lesion: Requires inferior petrosal sinus sampling (IPSS)
• 6-9 mm lesion: Gray zone - expert opinions differ; consider IPSS plus CRH/DDAVP testing

Medical Therapy for Cushing's Disease

Ketoconazole or metyrapone are first-line medical therapies 4:

• Ketoconazole: 400-1200 mg/day PO divided BID
  • Efficacy: ~65% UFC normalization initially
  • Monitor: Liver enzymes, watch for GI disturbances, gynecomastia, adrenal insufficiency
• Metyrapone: Block-and-replace regimens may be considered
• Pasireotide: Not recommended in children; osilodrostat trials ongoing 4

Monitor response with morning cortisol levels

Primary Aldosteronism

For confirmed primary aldosteronism, proceed with subtype differentiation 1:

When to Bypass Adrenal Venous Sampling (AVS)

Proceed directly to medical management without AVS if 1:

• Mild PA with likely bilateral disease
• Multiple comorbidities making surgery high-risk
• Patient preference for medical therapy

Exception for direct surgery without AVS: Age <35 years with marked PA, hypokalemia, and >1.0 cm unilateral adrenal adenoma on CT 1

Medical Management

Spironolactone is the first-line MRA due to low cost and widespread availability 1:

Initiation and titration algorithm 1:

1. Start spironolactone (dose based on hypertension severity)
2. Consider discontinuing other antihypertensives initially
3. Monitor: Potassium, renal function, renin, blood pressure
4. If BP not controlled and renin suppressed: Increase spironolactone dose to raise renin from baseline
5. If spironolactone contraindicated (hyperkalemia, advanced renal impairment, pregnancy): Use ENaC inhibitors (amiloride, triamterene) as second-line 1

All MRAs at equivalent potencies have similar efficacy; those with greater mineralocorticoid receptor specificity may have fewer androgen/progesterone-mediated side effects 1

Additional Screening

In patients with PA and adrenal adenoma, perform DST to screen for concurrent autonomous cortisol secretion 1:

• If cortisol >50 nmol/L (>1.8 μg/dL): Evaluate for Cushing's syndrome per guidelines
• For mild autonomous cortisol secretion, measure plasma metanephrines during follow-up 1

Mild Autonomous Cortisol Secretion (MACS)

All patients with MACS require screening for cortisol-related comorbidities: hypertension, type 2 diabetes, osteoporosis, cardiovascular disease 2

Surgical treatment should be considered in patients with MACS who have relevant comorbidities potentially attributable to cortisol excess 1, 2:

• Recent evidence shows superior cardiovascular and metabolic outcomes with surgery versus medical management alone in carefully selected patients 3
• The paradigm has shifted from treating secondary comorbidities medically to addressing underlying autonomous cortisol production surgically 3

Adrenal Incidentalomas

Growth surveillance is the third pillar 3:

• Growth rate >0.8 cm/year predicts malignancy
• Lesions >4 cm that are inhomogeneous or HU >20 warrant surgery due to sufficient malignancy risk 2

Follow-up for Nonsurgical Patients

Surgery is not indicated for asymptomatic, nonfunctioning unilateral masses with obvious benign imaging features 2, 5

For patients not undergoing surgery, implement structured surveillance (specific intervals not detailed in highest-quality guidelines but follow-up imaging and repeat hormonal testing are recommended) 2

Pheochromocytoma

Plasma-free metanephrines are the diagnostic test of choice 2

Over 35% of pheochromocytomas/paragangliomas have germline mutations; genetic testing should be offered to all patients 6

Treatment is complex and requires interdisciplinary management at specialized centers 6:

• Localized disease: Surgery is the only curative option
• Metastatic disease: Individualized decision between active surveillance, radionuclide therapy, sunitinib, or chemotherapy

Surgical Indications

Adrenalectomy is indicated for 2:

• Radiological suspicion of malignancy (HU >20, size >4 cm, inhomogeneous)
• Overt hormonal syndromes (overt Cushing's, pheochromocytoma, aldosterone-producing adenoma in surgical candidates)
• MACS with significant cortisol-related comorbidities (individualized approach)

Minimally invasive adrenalectomy is the gold standard surgical approach in experienced hands 3

Critical Management Principles

Refer patients to multidisciplinary centers of excellence for complex cases, particularly:

• Cushing's disease requiring specialized neurosurgery 4
• Suspected adrenocortical carcinoma (0.5-2 per million annually, 5-year survival only 50%, <15% if metastatic) 3
• Pheochromocytoma/paraganglioma requiring genetic counseling 6

Early diagnosis and expert management are critical given potential for long-term adverse health outcomes from prolonged hypercortisolism and morbidity from surgical interventions 4