Can Endocrine Dysfunction Be Reliably Tested in Aged Horses That Are Experiencing Pain?
Authors: Gehlen Heidrun, Jaburg Nina, Merle Roswitha, Winter Judith
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Endocrine Testing in Painful Aged Horses Distinguishing pituitary pars intermedia dysfunction (PPID) from pain-induced elevations in adrenocorticotropic hormone (ACTH) presents a genuine diagnostic challenge in geriatric equine practice, particularly when aged horses present with concurrent musculoskeletal or metabolic disease. Gehlen and colleagues investigated whether low to moderate pain intensity would compromise the reliability of basal ACTH measurement and the thyrotropin-releasing hormone (TRH) stimulation test by recruiting 15 horses across three disease categories—colic, laminitis, and orthopaedic conditions—and collecting endocrine samples whilst horses experienced pain, then repeating testing once pain had resolved. Neither basal nor stimulated ACTH concentrations differed significantly between painful and pain-free states, regardless of pain intensity or underlying diagnosis, though descriptive analysis suggested pain might blunt the TRH-stimulated ACTH response. These findings indicate that clinicians can confidently proceed with baseline ACTH measurement and TRH stimulation testing to investigate suspected PPID even when aged horses are managed through low to moderate pain, without expecting spuriously elevated results that would lead to overdiagnosis. However, practitioners should remain alert to potential TRH response dampening in painful patients and consider serial testing where clinical suspicion remains high.
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Practical Takeaways
- •Endocrine testing for PPID (ACTH and TRH stimulation) can proceed reliably in aged horses with low to moderate pain without invalidating results due to pain-induced false positives
- •Pain management should not be delayed while awaiting endocrine test results; diagnostic testing can be performed concurrently with pain treatment in these cases
- •Clinicians can confidently diagnose or rule out PPID using standard protocols even when horses are experiencing mild to moderate pain from colic, laminitis, or orthopedic conditions
Key Findings
- •No significant difference in basal or stimulated ACTH concentrations between horses with low to moderate pain and pain-free controls
- •No statistically significant differences in ACTH or cortisol across different pain intensities or disease groups
- •TRH stimulation test showed increased ACTH at 30 minutes post-application in treated pain group (p = 0.007), though this did not reach statistical confirmation across all analyses
- •ACTH measurement and TRH stimulation testing for PPID diagnosis appear feasible in horses experiencing low to moderate pain