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Journal of veterinary internal medicine2026; 40(1); aalaf056; doi: 10.1093/jvimsj/aalaf056

Assessment of baseline adrenocorticotropic hormone and insulin concentrations in healthy horses in Saskatchewan over a 1-year period.

Abstract: Endocrine disorders in horses, such as pituitary pars intermedia dysfunction and equine metabolic syndrome, rely on hormone testing for diagnosis, but seasonal and regional variabilities highlight the need for locally generated data. Objective: To characterize monthly blood concentrations of ACTH and insulin over 1 year in healthy horses in Saskatchewan. A secondary objective was to assess the association between these outcomes and the following factors: sex, age, breed, pregnancy status, level of exercise, body condition score, and cresty neck score. Methods: Sixty-eight clinically healthy, client- or university-owned horses. Methods: Prospective, observational study. Inclusion criteria: normal physical exams, no travel outside Saskatchewan, no ongoing endocrine or metabolic illness. Samples were collected monthly for 12 months. Blood concentrations of ACTH and insulin were determined by a chemiluminescence assay and associations with the explanatory variables were assessed using generalized estimating equations and generalized linear models. Results: The concentration of ACTH varied by age and month, with older horses showing greater seasonal fluctuations. Maximum ACTH concentration peaked in late summer and early fall, with the older horses and certain breeds showing higher concentrations. Insulin concentrations were highest in August and lowest in December, and consistently higher in Warmbloods than Quarter Horses. Conclusions: Our findings reveal month- and age-related effects on ACTH concentration, and month- and breed-related effects on insulin concentration in healthy horses. These findings support the need to consider temporal and signalment factors when interpreting endocrine test results.
© 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: 41742515PubMed Central: PMC12881943DOI: 10.1093/jvimsj/aalaf056Google 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 monitored the blood levels of two key hormones, ACTH and insulin, in healthy horses living in Saskatchewan throughout one year.
  • The goal was to understand how these hormone levels change with time and various horse characteristics to improve diagnosis of endocrine disorders.

Introduction

  • Endocrine disorders in horses, specifically pituitary pars intermedia dysfunction (PPID) and equine metabolic syndrome (EMS), are diagnosed by measuring hormones.
  • Hormone levels can vary by season and region, so local data is necessary for accurate diagnosis.
  • This study aimed to characterize monthly blood levels of ACTH (adrenocorticotropic hormone) and insulin in healthy Saskatchewan horses over one year.
  • A secondary aim was to explore how factors like sex, age, breed, pregnancy, exercise, body condition, and neck fat affect these hormone levels.

Materials and Methods

  • Sixty-eight clinically healthy horses, either client- or university-owned, were enrolled.
  • Selection criteria included thorough physical exams confirming health, no recent travel outside Saskatchewan, and no known endocrine or metabolic diseases.
  • Blood samples were collected monthly for 12 consecutive months.
  • ACTH and insulin concentrations were measured using a chemiluminescence assay, a sensitive laboratory method.
  • Statistical analyses involving generalized estimating equations and generalized linear models were used to test associations between hormones and horse characteristics.

Results

  • ACTH Concentrations:
    • ACTH levels changed depending on the month and the horse’s age.
    • Older horses showed larger seasonal fluctuations in ACTH.
    • ACTH concentrations peaked in late summer and early fall.
    • Certain breeds exhibited higher ACTH levels compared to others.
  • Insulin Concentrations:
    • Insulin levels were highest in August and lowest in December.
    • Warmblood horses consistently showed higher insulin levels than Quarter Horses.

Conclusions

  • The study found that ACTH levels in healthy horses vary by both season (month) and age.
  • Insulin levels vary by season and are influenced by breed.
  • These variations suggest that veterinarians should consider temporal (time of year) and signalment (horse-specific) factors such as age and breed when interpreting hormone test results.
  • Understanding these natural fluctuations aids in better diagnosis and management of endocrine disorders in horses living in Saskatchewan.

Cite This Article

APA
Viviani P, Ragno VM, Parker S, Montgomery JB. (2026). Assessment of baseline adrenocorticotropic hormone and insulin concentrations in healthy horses in Saskatchewan over a 1-year period. J Vet Intern Med, 40(1), aalaf056. https://doi.org/10.1093/jvimsj/aalaf056

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 40
Issue: 1
PII: aalaf056

Researcher Affiliations

Viviani, Paula
  • Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
  • Large Animal Teaching Hospital, Department of Clinical Sciences, Faculty of Veterinary Medicine, Universidad Nacional del Centro de la Provincia de Buenos Aires, Buenos Aires, Argentina.
Ragno, Valentina M
  • Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
  • Veterinary University Hospital, Faculty of Veterinary Medicine, University of Montreal, Quebec, Canada.
Parker, Sarah
  • Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
  • Center for Applied Epidemiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Montgomery, Julia B
  • Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
  • Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK, United States.

Grant Funding

  • Townsend Equine Health Research Fund (TEHRF)

Conflict of Interest Statement

The authors declare no conflict of interest.

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