Eleanor M. Kellon, VMD
Because testing for hormonal disease in horses is often triggered by the horse developing laminitis, the effect of pain on test results is always a concern.
Adrenocorticotropic (ACTH) testing is the first step in diagnosis of Pituitary Pars Intermedia Dysfunction (PPID)/Cushing’s Disease. Insulin testing is needed for diagnosing Equine Metabolic Syndrome (EMS) or Insulin Resistance (IR).
A 2020 German study(1) looked at hospitalized horses in pain from various conditions including colic, laminitis, and orthopedic conditions. All horses had been in the clinic for at least 24 hours. Horses were 15-years-old or younger with no clinical signs of PPID.
They were tested by both baseline ACTH and ACTH after Thyrotropin-releasing hormone (TRH) stimulation, both while in pain and after they had recovered. There was no difference in test results regardless of pain intensity, so no effect of pain in this study.
However, timing may be important. A 2001 study in healthy males(2) found acute pain resulted in markedly elevated cortisol and insulin resistance.
Since acute stress, wounds, etc., can cause the adrenal glands to release cortisol without ACTH increase, it's unclear from that study if acute pain will influence ACTH — although it certainly increases insulin.
To learn more, join the ECIR Group, August 13-15, for the 2021 NO Laminitis! Conference, via Zoom, which continues the mission to serve the scientific community, practicing clinicians, and owners by focusing on investigations most likely to quickly, immediately, and significantly benefit the welfare of the horse. www.nolaminitis.org <http://www.nolaminitis.org/>
1. Gehlen H, Jaburg N, Merle R, Winter J. Can Endocrine Dysfunction Be Reliably Tested in Aged Horses That Are Experiencing Pain?, Animals (Basel). 2020 Aug; 10(8): 1426. Published online 2020 Aug 14. doi: 10.3390/ani10081426
2. Greisen J, Juh C, Grøfte T, Vilstrup H, Jensen, T, Schmitz O. Acute Pain Induces Insulin Resistance in Humans Anesthesiology September 2001, Vol. 95, 578–584. https://doi.org/10.1097/00000542-200109000-00007 <https://doi.org/10.1097/00000542-200109000-00007>
THE MISSION of the ECIR Group Inc. is to improve the welfare of equines with metabolic disorders via a unique interface between basic research and real-life clinical experience. Prevention of laminitis is the ultimate goal. The ECIR Group serves the scientific community, practicing clinicians, and owners by focusing on investigations most likely to quickly, immediately, and significantly benefit the welfare of the horse.