Test Details for ACTH endogenous |
| Lab Section: | Endocrinology |
| Test Name: | ACTH endogenous |
| Description: | Endogenous; equine |
| Test Code: | ACTH |
| Fee: | 22.00 |
| Sample: | 1 mL EDTA plasma ONLY |
| Min Sample Volume: | |
| Collection Container: | glass or plastic |
| Coolant: | Freeze |
| Test Days: | M-F |
| Lag Time: | 1-3 days |
| Comments: | Plasma must be separated from cells and frozen within 4 hours. For more information, see AppendixC |
INTERPRETATION OF EQUINE ACTH TEST
ACTH: In Equine Cushing's Disease (Pituitary Pars Intermedia Dysfunction or PPID), the concentration of ACTH is greater than the reference values above. The higher the ACTH concentration is, the more likely is the diagnosis of PPID. However, because of the irregular patterns of ACTH secretion, the concentration may be within the reference range. A low ACTH concentration could be due to incorrect sample type or handling procedure, a normal low point during daily secretion, administration of exogenous steroids, or treatment with pergolide. Seasonal elevation of ACTH levels occurs from approximately mid-August to mid-October. Samples taken during this time period may have up to 3 times reference levels of ACTH in normal horses. Horses with PPID tend to have even higher ACTH concentrations in this time period, i.e., greater than 3 times reference. Horses exhibiting clinical signs of PPID, but with an ACTH that is within reference range, should be retested in 1 - 6 months or an alternate test should be considered. The dexamethasone-suppression test or the TRH response test is suggested if the ACTH level is not definitive. If equine metabolic syndrome is a possible diagnosis, insulin and leptin tests are recommended.
Precautions for ACTH:
Equine plasma concentrations of ACTH are affected by stress, exercise, and some drugs. ACTH is readily metabolized in whole blood and serum samples. Blood samples must be collected with EDTA as the anticoagulant. Samples should be kept chilled and plasma removed from cells within 4 hours after collection. Test results from samples left on cells longer than 4 hours should be interpreted with caution. Horses should not be exercised or stressed before drawing blood samples because exercise and stress can increase ACTH levels.
