|
TRH Stimulation Test – Horse (2 x ACTH)
Diagnosis
- Pituitary Pars Intermedia Dysfunction (PPID / Cushing’s disease)
- High sensitivity and specificity
- Recommended when ACTH measurement or suppression test results do not match clinical findings or are inconclusive
Species
Horse
Sample Material
EDTA plasma: 2 × 0.5 ml
Centrifuge, pipette off plasma, and cool promptly after collection
Test Procedure
- Collect first blood sample (baseline ACTH)
- Administer TRH intravenously:
- Horses > 250 kg: 1 mg
- Horses < 250 kg: 0.5 mg
- Collect second blood sample exactly 10 minutes after TRH injection (stimulated ACTH)
Parameter Measured
ACTH
Interpretation (January–June)
- < 100 pg/ml : Negative
- 100–220 pg/ml : Borderline
- > 200 pg/ml : Positive (PPID likely)
Seasonal Note
From July to December, ACTH levels naturally rise, leading to many false positives. During this period, the TRH stimulation test can only be used to confirm healthy horses, not to diagnose PPID.
|
