What is the recommended diagnostic and treatment approach for hypercortisolism (Cushing syndrome)?

Approach to Hypercortisolism

Begin diagnostic workup with at least 2-3 measurements of any combination of: 24-hour urinary free cortisol (UFC), late-night salivary cortisol (LNSC), or 1-mg overnight dexamethasone suppression test (DST), then proceed to determine ACTH-dependent vs ACTH-independent etiology, followed by surgical resection as first-line treatment for all confirmed cases 1.

Diagnostic Algorithm

Step 1: Initial Screening (Exclude Exogenous Glucocorticoids First)

The 2021 Lancet consensus guidelines emphasize that no single test is superior—selection depends on clinical context 1:

• DST (1-mg overnight): Preferred for shift workers or those with disrupted sleep schedules. Cortisol >5 μg/dL suggests hypercortisolism. Critical pitfall: Unreliable in women on oral estrogen (increases CBG), and with CYP3A4 inducers (phenobarbital, carbamazepine, St. John's wort) causing false positives. Consider measuring dexamethasone levels concurrently to reduce false positives 1.

• UFC (24-hour collections): Obtain 2-3 collections due to 50% intra-patient variability. Avoid in renal impairment (CrCl <60 mL/min) or polyuria (>5 L/24h) 1.

• LNSC: Collect 2-3 samples. Easier for patients than UFC. If adrenal tumor suspected, only use if cortisone levels can also be measured 1.

Step 2: Distinguish True Cushing's from Pseudo-Cushing's

If initial tests show mild elevations (UFC <3× upper limit of normal), consider pseudo-Cushing's from psychiatric disorders, alcohol use, PCOS, or obesity 1. Use:

• Dex-CRH test or desmopressin test to differentiate—both show good diagnostic performance, with desmopressin being less complex and expensive 1.

Step 3: Determine Etiology via ACTH Level

• ACTH suppressed: ACTH-independent (adrenal source—adenoma, carcinoma, hyperplasia)
• ACTH mid-normal to elevated: ACTH-dependent (pituitary Cushing's disease ~60-70% of cases, or ectopic ACTH) 2

Step 4: Localize Source

For ACTH-dependent cases:

• Pituitary MRI
• If imaging discordant/equivocal: Bilateral inferior petrosal sinus sampling (IPSS) is the gold standard 3
• High-dose dexamethasone suppression and CRH stimulation tests help distinguish pituitary from ectopic sources

For ACTH-independent cases:

• Adrenal CT or MRI

Treatment Algorithm

Primary Treatment: Surgery

Surgical removal of the cortisol-producing tumor is first-line treatment for ALL etiologies 1, 2, 4. This includes:

• Transsphenoidal resection for pituitary adenomas
• Adrenalectomy for adrenal tumors
• Resection of ectopic ACTH-secreting tumors

Medical Therapy Indications

Medical treatment is indicated when 1, 5, 4:

1. Patient not a surgical candidate or declines surgery
2. Preoperative control of severe hypercortisolism
3. Postoperative residual/recurrent disease
4. Awaiting effects of radiation therapy

Medical Therapy Selection Strategy

The 2021 consensus provides clear hierarchical recommendations based on disease severity 1:

For Mild Disease (No Visible Tumor on MRI):

• First choice: Ketoconazole, osilodrostat, or metyrapone (adrenal steroidogenesis inhibitors)
• Alternative: Cabergoline (slower onset, less effective, but convenient dosing)

For Mild-to-Moderate Disease (Residual Tumor Present):

• Prefer: Cabergoline or pasireotide (potential for tumor shrinkage)
• Critical caveat: Pasireotide causes high rates of hyperglycemia—careful patient selection required 1

For Severe Disease:

Rapid cortisol normalization is the primary goal 1:

• First-line: Osilodrostat or metyrapone (response within hours) or ketoconazole (response within days)
• If hospitalized/cannot take oral: Etomidate
• If inadequate response: Combination therapy with multiple steroidogenesis inhibitors
• If medical therapy fails: Proceed directly to bilateral adrenalectomy (BLA) to prevent worsening outcomes 1

Special Population Considerations:

• Young women desiring pregnancy: Metyrapone may be considered with precautions; target cortisol 1.5× ULN during pregnancy 1
• History of bipolar/impulse control disorder: Avoid cabergoline 1
• Mifepristone: Only for experienced clinicians—improves hyperglycemia and weight but worsens hypokalemia, no reliable cortisol monitoring, risk of adrenal insufficiency 1

Combination Therapy Regimens

When monotherapy inadequate 1:

• Ketoconazole + metyrapone: Maximizes adrenal blockade
• Ketoconazole + cabergoline: Rational if visible tumor present
• Consider triplet combinations in refractory cases

Monitoring Treatment

Use serial UFC and LNSC measurements to monitor treatment response 1. Target normalization of cortisol levels (or cortisol action if using mifepristone).

Critical Pitfalls to Avoid

1. Don't rely on single screening test—always obtain 2-3 measurements due to high variability 1
2. Check medication list carefully—many drugs interfere with testing (CYP3A4 inducers/inhibitors, oral estrogens) 1
3. Don't delay bilateral adrenalectomy in severe disease unresponsive to medical therapy—mortality risk increases 1
4. Mifepristone requires specialized expertise—cortisol levels cannot guide dosing or detect adrenal insufficiency 1
5. Monitor thyroid function closely during medical therapy and adjust replacement as needed 1
6. Lifelong monitoring required post-treatment to detect recurrence and manage comorbidities 6