Pilot study of β-endorphin concentrations in horses with pituitary pars intermedia dysfunction using a newly validated enzyme-linked immunosorbent assay

  • Domest Anim Endocrinol. 2025 Nov 26:95:106982. doi: 10.1016/j.domaniend.2025.106982.
N Fouché  1 ,  J Howard  2 ,  V Gerber  3 ,  P Billmann  3 ,  M Farinha do Sul  3 ,  G Christen  3 ,  R Bruckmaier  4 ,  C Philipona  4 ,  N Besuchet Schmutz  4 ,  J Gross  4
Affiliations
  • 1. Swiss Institute of Equine Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland. Electronic address: [email protected].
  • 2. Clinical Diagnostic Laboratory, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
  • 3. Swiss Institute of Equine Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
  • 4. Veterinary Physiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
PMID: 41317409 DOI: 10.1016/j.domaniend.2025.106982
Abstract

β-endorphin, a proopiomelanocortin (POMC)-derived peptide secreted by pars intermedia melanotropes, may play a significant but underexplored role in pituitary pars intermedia dysfunction (PPID) pathophysiology and diagnosis. This study aimed to (1) validate a commercially available human β-endorphin enzyme-linked immunosorbent assay (ELISA) kit for equine samples, and (2) compare β-endorphin concentrations between horses with PPID and healthy controls. Assay validation included the generation of standard curves using purified synthetic equine β-endorphin and human β-endorphin standards, with both curves showing full parallelism. Intra- and inter-assay coefficients of variation (CV) were determined by measuring 37 equine serum samples in duplicate on a single plate and five serum samples across seven different plates. The intra-assay CV was 11.3 % for standards and 5.3 % for equine samples, whereas the inter-assay CV was 6.9 % for standards and 15.6 % for equine samples. Plasma β-endorphin concentrations remained stable over 24 hours regardless of centrifugation timing, storage temperature, or duration. β-endorphin concentrations were determined in five horses with PPID and 20 healthy aged controls. Horses in the PPID group had significantly higher β-endorphin concentrations (median, 506 pg/mL; IQR, 213-762) compared to horses in the control group (median, 35 pg/mL; IQR, 16-55) (P < 0.001). This study may serve as a basis for further research on the role of β-endorphin in horses, particularly in horses with PPID.

Keywords
Adrenocorticotropic hormone; Endocrine disorder; Equine; Geriatric; PPID.
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