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Reference: Cushing Syndrome Etiologies
Diagnostic Flowchart (Click to Zoom)
Comparison Table
| Etiology | ACTH | Cortisol | High-Dose Dex Test |
|---|---|---|---|
| Pituitary Adenoma (Cushing Disease) | ↑ High | ↑ High | Suppresses (>50% drop) |
| Ectopic ACTH (e.g., Small Cell Lung Cancer) | ↑ High | ↑ High | No Change |
| Adrenal Tumor (Adenoma/Carcinoma) | ↓ Low | ↑ High | No Change (N/A) |
| Exogenous Steroids (e.g., Prednisone) | ↓ Low | ↓ Low* | No Change (N/A) |
Tips & Mnemonics
Mnemonic: "High Dose" Logic
• Pituitary = Plus suppression.
• Ectopic = Escape (No suppression).
• Adrenal = ACTH absent.
• Pituitary = Plus suppression.
• Ectopic = Escape (No suppression).
• Adrenal = ACTH absent.