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Home / Equine Research Bank / J Vet Intern Med / Associations among beta-endorphin, ACTH, cortisol concentrat...
Journal of veterinary internal medicine2026; 40(1); aalag023; doi: 10.1093/jvimsj/aalag023

Associations among beta-endorphin, ACTH, cortisol concentration, age, and clinical signs indicative of pituitary pars intermedia dysfunction in geriatric horses.

Abstract: Limited published data are available regarding the relationships among clinical signs associated with pituitary pars intermedia dysfunction (PPID), age, and concentrations of proopiomelanocortin-derived peptides and cortisol. Objective: Identify clinical signs associated with age, beta-endorphin (β-END), adrenocorticotropic hormone (ACTH), and cortisol concentrations and compare β-END and cortisol concentrations between horses with PPID and geriatric controls. Methods: A total of 113 horses aged 18-32 years. Methods: Cross-sectional study. Clinical signs were scored, plasma β-END, ACTH, and serum cortisol concentrations were measured, and their associations were evaluated. Horses were classified as PPID or controls based on haircoat abnormalities and ACTH concentrations, and group comparisons were performed. Results: Increased β-END and ACTH concentrations were associated with haircoat abnormalities (P < .001), whereas advanced age was associated with muscle atrophy, weight loss, and lethargy (P < .001). Cortisol concentrations were not associated with any of the clinical signs. The β-END concentrations were higher in the PPID group (median, 291 pg/mL; interquartile range [IQR], 122-836 pg/mL; n = 40) compared with the control group (median, 55.0 pg/mL; IQR, 45.0-68.0 pg/mL; n = 53; P < .001). Conclusions: In this geriatric study cohort, haircoat abnormalities were associated with increased β-END and ACTH concentrations, whereas other clinical signs, such as muscle atrophy, weight loss, and lethargy, were primarily linked to age. Because PPID is diagnosed based on clinical signs and ACTH concentrations, it is important to distinguish clinical signs that are age-related from those associated with PPID.
© The Author(s) 2026. Published by Oxford University Press on behalf of the American College of Veterinary Internal Medicine.
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Publication Date: 2026-02-26 PubMed ID: 41742592PubMed Central: PMC12927883DOI: 10.1093/jvimsj/aalag023Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study investigates the relationships between clinical signs of pituitary pars intermedia dysfunction (PPID), age, and hormone concentrations (beta-endorphin, ACTH, and cortisol) in older horses.
  • The research aims to differentiate which clinical signs are related to PPID versus those simply related to aging in geriatric horses.

Background

  • PPID is a common endocrine disorder in older horses involving the pituitary gland’s pars intermedia.
  • Clinical signs of PPID often overlap with normal aging signs, making diagnosis challenging.
  • Key hormones related to PPID include proopiomelanocortin (POMC)-derived peptides such as ACTH and beta-endorphin (β-END), as well as cortisol.
  • Previous literature has limited data on how these hormones relate to clinical signs and age in older horses.

Objectives

  • Evaluate associations among clinical signs suggestive of PPID, age, and concentrations of β-END, ACTH, and cortisol.
  • Compare β-END and cortisol levels between horses diagnosed with PPID and geriatric controls.

Methods

  • Study Design: Cross-sectional study involving 113 horses aged 18 to 32 years.
  • Clinical signs were scored and documented for each horse.
  • Blood samples were collected to measure plasma β-END, ACTH, and serum cortisol concentrations.
  • Horses were classified into PPID or control groups based on haircoat condition and ACTH levels.
  • Statistical analyses evaluated associations between hormone concentrations, age, and clinical signs, and compared hormone levels between groups.

Key Results

  • Higher β-END and ACTH concentrations showed a strong association with haircoat abnormalities (P<.001), a classic sign of PPID.
  • Advanced age was significantly associated with muscle atrophy, weight loss, and lethargy (P<.001), which are general aging signs rather than PPID-specific.
  • Cortisol concentrations did not show association with any clinical signs examined.
  • The PPID group exhibited markedly higher median β-END concentrations (291 pg/mL) compared to controls (55 pg/mL), confirming a hormonal difference between disease and normal aging.

Interpretation

  • Haircoat abnormalities in older horses likely indicate increased β-END and ACTH, consistent with PPID pathology.
  • Other signs like muscle wasting, weight loss, and lethargy tend to reflect the natural aging process rather than the disease.
  • Cortisol does not appear to be a useful marker for distinguishing PPID-related clinical signs in geriatric horses.
  • Elevated β-END might be a supportive diagnostic biomarker for PPID when combined with ACTH levels and clinical evaluation.

Conclusions and Clinical Implications

  • Veterinarians should carefully differentiate clinical signs caused by PPID from those resulting from normal aging to avoid misdiagnosis.
  • Testing ACTH and β-END concentrations alongside clinical assessment of haircoat can improve PPID diagnosis accuracy in older horses.
  • This study emphasizes the importance of recognizing specific hormone patterns linked to PPID versus aging symptoms in geriatric equine patients.

Cite This Article

APA
Billmann P, Durham A, Christen G, Savioli G, Gross JJ, Gerber V, Fouché NE. (2026). Associations among beta-endorphin, ACTH, cortisol concentration, age, and clinical signs indicative of pituitary pars intermedia dysfunction in geriatric horses. J Vet Intern Med, 40(1), aalag023. https://doi.org/10.1093/jvimsj/aalag023

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 40
Issue: 1
PII: aalag023

Researcher Affiliations

Billmann, Paula
  • Swiss Institute of Equine Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
Durham, Andy
  • Liphook Equine Hospital, Liphook, Hampshire, United Kingdom.
Christen, Garance
  • Swiss Institute of Equine Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
Savioli, Giulia
  • Veterinary Public Health Institute, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
  • Federal Food Safety and Veterinary Office, Bern, Switzerland.
Gross, Josef Johann
  • Veterinary Physiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
Gerber, Vinzenz
  • Swiss Institute of Equine Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
Fouché, Nathalie Elisa
  • Swiss Institute of Equine Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.

Grant Funding

  • Vontobel Foundation
  • Vetsuisse Faculty, University of Bern
  • Internal Research Funds
  • ISMEquine Research No. 33-890 / Swiss Institute of Equine Medicine, Bern, Switzerland

Conflict of Interest Statement

A.D. is employed by Liphook Equine Hospital which offers commercial laboratory services for horses.

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