Curated insights • How it Works • Practical Pearls • Evidence Base
| Test | Abnormal Threshold | Notes |
|---|---|---|
| 1mg Overnight DST | 8AM Cortisol > 1.8 µg/dL | Most sensitive. Oral contraceptives cause false positives. |
| 24h UFC | > ULN (Upper Limit of Normal) | Needs 2 collections. CKD (eGFR < 60) decreases sensitivity. |
| Late-Night Salivary | > ULN (~145 ng/dL) | Loss of circadian rhythm. Needs 2 collections. Sleep patterns matter. |
The diagnosis of Cushing's syndrome: an Endocrine Society Clinical Practice Guideline.
Endocrine Society guidelines recommend at least TWO abnormal screening tests (even from the same modality) to establish a "biochemical diagnosis" of Cushing\'s Syndrome before proceeding to localization (ACTH testing/Imaging).