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The effect of geographic location, breed, and pituitary dysfunction on seasonal adrenocorticotropin and α-melanocyte-stimulating hormone plasma concentrations in horses.
Abstract: Plasma α-melanocyte-stimulating hormone (α-MSH) and adrenocorticotropin (ACTH) concentrations in horses vary with season, confounding diagnostic testing for pituitary pars intermedia dysfunction (PPID). Objective: The goals of this study were to determine whether seasonal variation in plasma α-MSH and ACTH concentrations in horses is influenced by geographic location, breed, or PPID. Methods: Healthy light breed horses residing in Florida, Massachusetts, and Finland (n = 12 per group); healthy Morgan horses (n = 13); healthy ponies (n = 9) and horses with PPID (n = 8). Methods: Monthly plasma α-MSH and ACTH concentrations were measured by radioimmunoassay. Nonlinear regression analysis was used to estimate the time of peak hormone concentrations. Mean hormone concentrations in fall and nonfall months were compared. Results: The fall peak plasma α-MSH concentration occurred earlier in horses residing at more northern locations. Mean seasonal α-MSH concentrations were similar in all healthy groups at all locations, but in the fall, plasma ACTH concentrations were higher in horses living in more southern locations. Plasma ACTH but not α-MSH concentrations were higher in Morgan horses compared with light breed horses from the same location. Hormone concentrations of ponies did not differ from those of horses during either season. Concentrations of both hormones were high in the fall compared with the spring in horses with PPID. Conclusions: These findings suggest geographic location of residence and breed may affect the onset, amplitude, or both of the seasonal peak of pars intermedia (PI) hormones and should be considered when performing diagnostic testing for PPID. Horses with PPID maintain seasonal regulation of PI hormone output.
Copyright © 2011 by the American College of Veterinary Internal Medicine.
Publication Date: 2011-07-11 PubMed ID: 21745243DOI: 10.1111/j.1939-1676.2011.0745.xGoogle Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
- Animal Health
- Animal Studies
- Breed Differences
- Clinical Study
- Comparative Study
- Diagnosis
- Diagnostic Technique
- Disease Diagnosis
- Endocrine System
- Epidemiology
- Equine Health
- Geographical Differences
- Hormones
- Horses
- Immunoassay
- Physiology
- Pituitary Pars Intermedia Dysfunction
- Plasma
- Regression Analysis
- Seasonal Variation
- Veterinary Medicine
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.
This research investigates whether the levels of the pituitary hormones ACTH and α-MSH in healthy horses and horses with a particular brain disorder (PPID) vary according to the season, the breed of the horse, and the geographic location of the horse. The results suggest that both season and location can influence hormone levels, and that this should be taken into account when diagnosing PPID.
Study Methodology
- The researchers studied various groups of horses. These included healthy light breed horses from Florida, Massachusetts, and Finland, healthy Morgan horses, healthy ponies, and horses with pituitary pars intermedia dysfunction (PPID).
- The study was designed to investigate whether differences in season, breed, geographic location, and health status influenced the hormone concentrations in the horses.
- Monthly measurements were taken of the plasma α-melanocyte-stimulating hormone (α-MSH) and adrenocorticotropin (ACTH) concentrations using a scientific test called radioimmunoassay.
- The researchers used a statistical method called nonlinear regression analysis to estimate when the hormone concentrations were at their highest.
Study Findings
- The researchers found that the time of peak plasma α-MSH concentration occurred earlier in horses living in northern locations.
- Also, the mean plasma ACTH concentrations during the fall were observed higher in southern locations as compared to others.
- Hormone concentrations in Morgan horses were higher than those in light breed horses from the same location, though for α-MSH, there weren’t any significant differences amongst different breed.
- The ponies’ hormone levels were at par with those of the horses in both seasons.
- In horses with PPID, concentrations of both hormones were high in the fall compared to the spring.
Study Conclusions
- The findings suggest that the geographic location and breed of the horse can influence the onset and amplitude (level) of the seasonal peak of pars intermedia (PI) hormones.
- Differences in the geographic location of the horse and its breed should therefore be considered when performing diagnostic tests for PPID.
- Even in sick horses (PPID), normal seasonal regulation of hormone output still occurs.
Cite This Article
APA
McFarlane D, Paradis MR, Zimmel D, Sykes B, Brorsen BW, Sanchez A, Vainio K.
(2011).
The effect of geographic location, breed, and pituitary dysfunction on seasonal adrenocorticotropin and α-melanocyte-stimulating hormone plasma concentrations in horses.
J Vet Intern Med, 25(4), 872-881.
https://doi.org/10.1111/j.1939-1676.2011.0745.x Publication
Researcher Affiliations
- Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA. diannem@okstate.edu
MeSH Terms
- Adrenocorticotropic Hormone / blood
- Animals
- Female
- Finland
- Florida
- Horses / blood
- Male
- Massachusetts
- Pituitary Gland, Intermediate / physiopathology
- Regression Analysis
- Seasons
- alpha-MSH / blood
Citations
This article has been cited 14 times.- DeNotta S, McFarlane D. Immunosenescence and inflammaging in the aged horse. Immun Ageing 2023 Jan 6;20(1):2.
- Karikoski NP, Box JR, Mykkänen AK, Kotiranta VV, Raekallio MR. Variation in insulin response to oral sugar test in a cohort of horses throughout the year and evaluation of risk factors for insulin dysregulation. Equine Vet J 2022 Sep;54(5):905-913.
- Mazzola SM, Colombani C, Pizzamiglio G, Cannas S, Palestrini C, Costa ED, Gazzonis AL, Bionda A, Crepaldi P. Do You Think I Am Living Well? A Four-Season Hair Cortisol Analysis on Leisure Horses in Different Housing and Management Conditions. Animals (Basel) 2021 Jul 20;11(7).
- de Laat MA, Reiche DB, Sillence MN, McGree JM. Incidence and risk factors for recurrence of endocrinopathic laminitis in horses. J Vet Intern Med 2019 May;33(3):1473-1482.
- Bertolesi GE, Zhang JZ, McFarlane S. Plasticity for colour adaptation in vertebrates explained by the evolution of the genes pomc, pmch and pmchl. Pigment Cell Melanoma Res 2019 Jul;32(4):510-527.
- de Laat MA, Sillence MN, Reiche DB. Phenotypic, hormonal, and clinical characteristics of equine endocrinopathic laminitis. J Vet Intern Med 2019 May;33(3):1456-1463.
- Spelta CW. Equine pituitary pars intermedia dysfunction: current perspectives on diagnosis and management. Vet Med (Auckl) 2015;6:293-300.
- Secombe CJ, Tan RHH, Perara DI, Byrne DP, Watts SP, Wearn JG. The Effect of Geographic Location on Circannual Adrenocorticotropic Hormone Plasma Concentrations in Horses in Australia. J Vet Intern Med 2017 Sep;31(5):1533-1540.
- Hart KA, Wochele DM, Norton NA, McFarlane D, Wooldridge AA, Frank N. Effect of Age, Season, Body Condition, and Endocrine Status on Serum Free Cortisol Fraction and Insulin Concentration in Horses. J Vet Intern Med 2016 Mar-Apr;30(2):653-63.
- Rendle DI, Duz M, Beech J, Parkin T, Durham AE. Investigation of single and paired measurements of adrenocorticotropic hormone for the diagnosis of pituitary pars intermedia dysfunction in horses. J Vet Intern Med 2015 Jan;29(1):355-61.
- Menzies-Gow NJ. Equine Pituitary Pars Intermedia Dysfunction. Vet Sci 2025 Aug 20;12(8).
- Vaughn SA, Lemons MB, Hart KA. The Effect of Season and Breed on Hypothalamic-Pituitary-Adrenal Axis Hormones, Metabolic Hormones, and Oxidative Markers in Ponies and Horses. J Vet Intern Med 2025 Mar-Apr;39(2):e70047.
- Viviani P, Lavado RA, Chavarria NH, Ragno VM, Montgomery JB. Spring and fall blood concentrations of adrenocorticotropic hormone, insulin, and thyroxine in healthy horses in Saskatchewan. Can Vet J 2024 Apr;65(4):335-342.
- Mendoza FJ, Toribio RE, Perez-Ecija A. Metabolic and Endocrine Insights in Donkeys. Animals (Basel) 2024 Feb 10;14(4).
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