What is the recommended approach to screen for hypercortisolism in patients with resistant hypertension, unexplained weight gain, central obesity, facial rounding, striae, proximal muscle weakness, osteoporosis, glucose intolerance, or an adrenal incidentaloma?

Screening for Hypercortisolism

Screen patients with resistant hypertension, unexplained weight gain with central obesity, facial rounding, striae, proximal muscle weakness, osteoporosis, glucose intolerance, or adrenal incidentaloma using any of three first-line tests: overnight 1-mg dexamethasone suppression test (DST), 24-hour urinary free cortisol (UFC), or late-night salivary cortisol (LNSC), with DST being the most practical initial choice for most patients. 1

Who to Screen

Do not screen all patients with obesity, diabetes, or hypertension. Target screening to high-risk populations:

• Resistant hypertension (requiring ≥3 antihypertensive agents including a diuretic, or ≥4 agents to achieve control) - prevalence of hypercortisolism reaches 27-37% in this group 2, 3
• Adrenal incidentaloma - 17% of confirmed Cushing's syndrome cases present this way 4
• Multiple progressive features: Recent weight gain (not just obesity), central adiposity, facial rounding, wide purple striae, proximal myopathy, osteoporosis, and glucose intolerance occurring together 4
• Difficult-to-control type 2 diabetes with multiple antihypertensive medications - up to 24% prevalence 2, 3

Key distinction: Recent weight gain is more predictive than obesity alone - obesity without CS was actually more common in patients where CS was ruled out (30% vs 4%) 4. Age and recent weight gain are significant predictors 5.

First-Line Screening Tests

Choose from three options based on clinical context 1:

1. Overnight 1-mg Dexamethasone Suppression Test (DST)

• Preferred for: Shift workers, disrupted sleep schedules, adrenal incidentalomas, and most general screening
• Method: Give 1 mg dexamethasone at 11 PM-midnight, measure serum cortisol at 8-9 AM
• Interpretation: Cortisol >1.8 μg/dL (50 nmol/L) suggests autonomous cortisol secretion; >5 μg/dL indicates overt hypercortisolism in incidentaloma patients 1
• Advantage: Single test, convenient, independent of patient collection accuracy

Critical pitfalls with DST:

• False positives: CYP3A4 inducers (phenobarbital, carbamazepine, St. John's wort), oral estrogens, pregnancy, chronic active hepatitis (all increase cortisol-binding globulin) 1
• False negatives: CYP3A4 inhibitors (fluoxetine, cimetidine, diltiazem), nephrotic syndrome, low albumin 1
• Solution: Measure dexamethasone levels simultaneously with cortisol to confirm adequate absorption and compliance 1

2. 24-Hour Urinary Free Cortisol (UFC)

• Preferred for: Patients on oral estrogens (where DST unreliable), when CBG alterations suspected
• Method: Collect 2-3 separate 24-hour urine samples 1
• Interpretation: Mean UFC >3-fold upper limit of normal strongly suggests true hypercortisolism; mild elevations may represent pseudo-Cushing's 1
• Advantage: Independent of CBG changes and dexamethasone compliance

Critical pitfalls with UFC:

• Requires accurate patient collection (major limitation)
• Variability up to 50% between collections 1
• Avoid in: Renal impairment (CrCl <60 mL/min) or polyuria (>5 L/24h) - use LNSC instead 1
• Influenced by: Sex, BMI, age, urinary volume, sodium intake 1

3. Late-Night Salivary Cortisol (LNSC)

• Preferred for: Renal impairment, polyuria, when multiple samples needed easily
• Method: Collect saliva samples at 11 PM-midnight on 2-3 separate nights
• Advantage: Easy patient collection, multiple samples feasible, detects loss of circadian rhythm
• For adrenal tumors: Also measure cortisone levels if using LNSC 1

Algorithmic Approach

1. Identify high-risk patient (resistant hypertension, adrenal incidentaloma, multiple progressive features)

2. Choose initial screening test:

   • DST for most patients, shift workers, adrenal incidentalomas
   • UFC if on oral estrogens or CBG alterations suspected (need 2-3 collections)
   • LNSC if renal impairment (CrCl <60) or polyuria (>5 L/24h)

3. Check for interfering factors before testing:

   • Medications affecting CYP3A4
   • Oral estrogens, pregnancy
   • Renal/hepatic disease
   • Psychiatric disorders, alcohol use (pseudo-Cushing's)

4. If abnormal: Repeat testing with same or different modality - no single test is definitive 1

5. If persistently abnormal: Proceed to confirmatory testing (Dex-CRH or desmopressin test) to distinguish true CS from pseudo-Cushing's, especially if elevations are mild 1

Distinguishing True vs Pseudo-Cushing's

Psychiatric disorders, alcohol use, PCOS, and obesity can activate the HPA axis, producing mildly abnormal screening tests (pseudo-Cushing's). Key features 1:

• Pseudo-Cushing's: UFC almost always <3-fold upper limit of normal
• True CS: More marked elevations, progressive features
• Confirmatory tests: Dex-CRH test or desmopressin test distinguish between them with good agreement 1

Prevalence Context

Recent large-scale studies reveal hypercortisolism is far more common than historically recognized: 24% in difficult-to-control diabetes with hypertension, 27% in resistant hypertension specifically 2, 3. In broader diabetes cohorts, confirmed CS ranges 0.6-3.4%, but abnormal DST occurs in 14-23% 2, 5. This means approximately 1 in 7 abnormal DST results leads to confirmed CS 5, emphasizing the need for systematic follow-up of positive screens.