Seasonal elevation in equine adrenocorticotropic hormone occurs throughout the contiguous United States and is influenced by latitude and age.
Abstract: To determine whether seasonal variation in equine plasma ACTH concentrations is affected by latitude between 29.7°N and 45.0°N in the US. Unassigned: A cohort study was performed between June 2019 and May 2020 in which plasma ACTH was measured monthly by chemiluminescence immunoassay. The study involved 201 apparently healthy horses from 9 locations within the US classified into northern, central, and southern latitude cohorts. Data analysis was performed with 3 major objectives: (1) identify outlier ACTH concentrations and horses; (2) estimate ACTH upper reference limits to define expected ACTH concentrations in healthy horses; and (3) identify factors influencing ACTH concentrations using linear mixed-effects regression models. Unassigned: Following outlier analysis, 154 horses remained from 3 latitude cohorts: northern (n = 29), central (84), and southern (41). Concentrations of ACTH were highest during late August and September and early October for all latitude cohorts. In horses over 15 years of age, ACTH was higher than in younger horses year-round, with a greater magnitude of increase during the seasonal elevation in ACTH. Unassigned: A seasonal elevation in ACTH occurred in horses throughout the contiguous US, with lower ACTH in horses in the southern compared to central cohort. Further investigation is required to determine the influence of latitude on horses that reside closer to the equator and the role of the changing photoperiod coinciding with the start of seasonal elevation in equine ACTH. Unassigned: Season and age should be considered when interpreting baseline ACTH concentrations in horses throughout the contiguous US.
Publication Date: 2025-08-01 PubMed ID: 40749730DOI: 10.2460/javma.25.04.0223Google Scholar: Lookup
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Summary
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The research article explores the seasonal changes in equine adrenocorticotropic hormone (ACTH) levels and investigates the influence of latitude and age on this hormonal variation using a cohort consisting of healthy horses from different geographic locations within the U.S.
Study Design and Objectives
- The study was conducted from June 2019 to May 2020 with a cohort of 201 horses from 9 different locations within the United States. These locations were further divided into groups according to latitude: northern, central, and southern.
- ACTH concentration was tested monthly using a chemiluminescent immunoassay, a technique that uses light emission to measure the concentration of hormones in the blood.
- The study aimed to identify outliers in ACTH concentrations and horses, estimate an upper limit for normal ACTH concentrations in healthy horses and determine factors affecting these hormonal levels through linear mixed-effects regression models.
Results of the Research
- Following the outlier analysis, 154 horses from the northern, central and southern cohorts remained in the study.
- Researchers found that ACTH concentrations were the highest during late August and September as well as early October across all latitude cohorts.
- A higher ACTH level was found in horses aged 15 years and above throughout the year, with a significant increase observed during the seasonal elevation.
Interpretation and Further Exploration
- The study concluded that a seasonal rise in ACTH occurred in horses throughout the various geographical locations in the United States. Horses in the southern cohort had lower ACTH levels compared to the central cohort.
- Further exploration will be focused on examining the influence of latitude on horses that reside closer to the equator and understanding how the changing photoperiod might affect the onset of ACTH elevation.
- The findings imply that both season and age should be considered when interpreting baseline ACTH concentrations in horses across different areas.
Cite This Article
APA
Pinn-Woodcock TL, Llanos-Soto SG, Ivanek R, Goodrich E, Frye E, Wells A, Mullen K, Arbittier E, Hughes L, Berryhill E, Brosnahan P, Buslinger L, Schnabel L, DeNotta S, Mallicote M, Peek S, Place NJ.
(2025).
Seasonal elevation in equine adrenocorticotropic hormone occurs throughout the contiguous United States and is influenced by latitude and age.
J Am Vet Med Assoc, 1-10.
https://doi.org/10.2460/javma.25.04.0223 Publication
Researcher Affiliations
- 1Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY.
- 1Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY.
- 1Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY.
- 1Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY.
- 1Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY.
- 1Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY.
- 2Department of Genetics, School of Medicine, University of North Carolina, Chapel Hill, NC.
- 3Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA.
- 4Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN.
- 5Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA.
- 6Animal Health Institute, Midwestern University, Glendale, AZ.
- 7Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC.
- 7Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC.
- 8Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL.
- 8Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL.
- 9Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI.
- 1Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY.
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