Influence of feeding status, time of the day, and season on baseline adrenocorticotropic hormone and the response to thyrotropin releasing hormone-stimulation test in healthy horses.
Abstract: Equine pituitary pars intermedia function can be assessed by the measurement of baseline and thyrotropin releasing hormone (TRH)-induced concentrations of adrenocorticotropic hormone (ACTH); however, these measurements may be affected by the environment. Therefore, a prospective observational study evaluated the influence of feeding, time of the day, and season on baseline and TRH-induced concentrations of ACTH in healthy horses. Baseline ACTH was measured in 50 horses before and 2 h after feeding. Six research horses were subjected to a crossover study in which 6 TRH tests were performed in 2 different seasons, March-April (MA) and July-September (JS), at 2 different times of the day, 8 AM and 8 PM, and, under 2 different conditions relative to feeding status, fasted and 2 h after feeding. Differences between fasted and fed horses were found in baseline ACTH, 17.1 ± 1.8 versus 46.1 ± 7.6 pg/mL (P = 0.003) and TRH-stimulated ACTH: 124.1 ± 21.3 versus 192.6 ± 33.1 pg/mL (P = 0.029) at 10 min, and 40.1 ± 4.9 versus 73.2 ± 13.4 pg/mL (P = 0.018) at 30 min post TRH injection. No differences were found between tests performed at different times of the day. Basal ACTH concentrations were greater in JS than in MA, 17.1 ± 1.8 versus 11.9 ± 0.6 pg/mL (P = 0.006). A seasonal influence was also found in stimulated ACTH values, which were much greater in JS 122.7 ± 36.7 versus 31.2 ± 7.4 pg/mL, at 10 min (P = 0.03) and 39.0 ± 7.2 versus 19.8 ± 3.1 pg/mL, at 30 min (P = 0.03). In addition to season, feeding is a potential confounding factor when measuring baseline or stimulated ACTH in horses. In conclusion, feeding status should be standardized for the diagnosis of equine pituitary pars intermedia dysfunction.
Copyright © 2014 Elsevier Inc. All rights reserved.
Publication Date: 2014-03-05 PubMed ID: 24906932DOI: 10.1016/j.domaniend.2014.02.004Google Scholar: Lookup
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- Clinical Trial
- Journal Article
- Adrenocorticotropic Hormone (ACTH)
- Animal Health
- Clinical Study
- Diagnosis
- Diagnostic Technique
- Disease Diagnosis
- Endocrine System
- Equine Health
- Equine Science
- Feeding Practices
- Hormones
- Horses
- Metabolism
- Observational Study
- Physiology
- Pituitary Pars Intermedia Dysfunction
- Seasonal Variation
- Thyrotropin-Releasing Hormone
- Veterinary Medicine
- Veterinary Research
Summary
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The research article investigates how changes in feeding, time of day, and season affect the hormones produced by the pituitary gland in horses, which could influence the diagnosis of equine pituitary gland dysfunction.
Context and Objective
- The study aims to determine how variations in feeding habits, the time of the day, and the season might influence the baseline and TRH (Thyrotropin Releasing Hormone)-induced production of ACTH (Adrenocorticotropic Hormone) in the pituitary gland of horses.
- This is significant because ACTH measurement is commonly used to assess pituitary function in horses, particularly for diagnosing equine pituitary pars intermedia dysfunction.
Methodology
- The study involved 50 healthy horses in which baseline ACTH was measured before and 2 hours after feeding.
- On top of that, six horses underwent a more intensive cross-over study wherein six TRH tests were performed under different conditions: two distinct seasons (March-April and July-September), two separate times of day (8 AM and 8 PM), and both in fasted state and 2 hours post-feeding.
Findings
- The results showed noticeable differences in both baseline and TRH-stimulated ACTH levels between fasted and fed horses. Specifically, both baseline and TRH-induced ACTH were higher in horses after they had been fed than when they were fasting.
- However, the time of day did not significantly alter the outcome of the tests.
- Seasonality was found to impact the concentration of basal ACTH with higher levels recorded in the July-September season than in the March-April season.
- Furthermore, the response of the horses to TRH – evidenced by their ACTH levels – was considerably larger in the July-September period compared to the March-April period.
Conclusion
- The study deduces that both seasonality and feeding status introduce potential confounding factors when it comes to measuring the baseline or TRH-stimulated ACTH level in horses.
- Therefore, these variables should be standardized while diagnosing equine pituitary pars intermedia disorder to ensure accurate results.
Cite This Article
APA
Diez de Castro E, Lopez I, Cortes B, Pineda C, Garfia B, Aguilera-Tejero E.
(2014).
Influence of feeding status, time of the day, and season on baseline adrenocorticotropic hormone and the response to thyrotropin releasing hormone-stimulation test in healthy horses.
Domest Anim Endocrinol, 48, 77-83.
https://doi.org/10.1016/j.domaniend.2014.02.004 Publication
Researcher Affiliations
- Department Medicina y Cirugía Animal, University of Cordoba, Campus Universitario Rabanales, Cordoba, Spain.
- Department Medicina y Cirugía Animal, University of Cordoba, Campus Universitario Rabanales, Cordoba, Spain.
- Department Medicina y Cirugía Animal, University of Cordoba, Campus Universitario Rabanales, Cordoba, Spain.
- Department Medicina y Cirugía Animal, University of Cordoba, Campus Universitario Rabanales, Cordoba, Spain.
- Laboratorio Veterinario Garfia S.L, Pol. Ind. Técnocordoba, Cordoba, Spain.
- Department Medicina y Cirugía Animal, University of Cordoba, Campus Universitario Rabanales, Cordoba, Spain. Electronic address: eaguilera@uco.es.
MeSH Terms
- Adrenocorticotropic Hormone / blood
- Animals
- Circadian Rhythm
- Europe
- Female
- Food Deprivation
- Horses / physiology
- Male
- Seasons
- Thyrotropin-Releasing Hormone / pharmacology
Citations
This article has been cited 13 times.- Drozdzewska K, Gehlen H. Markers for internal neoplasia in the horse. Vet Med Sci 2023 Jan;9(1):132-143.
- Kirkwood NC, Hughes KJ, Stewart AJ. Prospective Case Series of Clinical Signs and Adrenocorticotrophin (ACTH) Concentrations in Seven Horses Transitioning to Pituitary Pars Intermedia Dysfunction (PPID). Vet Sci 2022 Oct 17;9(10).
- Kirkwood NC, Hughes KJ, Stewart AJ. Pituitary Pars Intermedia Dysfunction (PPID) in Horses. Vet Sci 2022 Oct 10;9(10).
- Thane K, Uricchio C, Frank N. Effect of early or late blood sampling on thyrotropin releasing hormone stimulation test results in horses. J Vet Intern Med 2022 Mar;36(2):770-777.
- 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.
- Horn R, Stewart AJ, Jackson KV, Dryburgh EL, Medina-Torres CE, Bertin FR. Clinical implications of using adrenocorticotropic hormone diagnostic cutoffs or reference intervals to diagnose pituitary pars intermedia dysfunction in mature horses. J Vet Intern Med 2021 Jan;35(1):560-570.
- Gehlen H, Schwarz B, Bartmann C, Gernhardt J, Stöckle SD. Pituitary Pars Intermedia Dysfunction and Metabolic Syndrome in Donkeys. Animals (Basel) 2020 Dec 8;10(12).
- Horn R, Bertin FR. Evaluation of combined testing to simultaneously diagnose pituitary pars intermedia dysfunction and insulin dysregulation in horses. J Vet Intern Med 2019 Sep;33(5):2249-2256.
- Hodge E, Kowalski A, Torcivia C, Lindborg S, Stefanovski D, Hart K, Frank N, van Eps A. Effect of thyrotropin-releasing hormone stimulation testing on the oral sugar test in horses when performed as a combined protocol. J Vet Intern Med 2019 Sep;33(5):2272-2279.
- 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.
- Menzies-Gow NJ. Equine Pituitary Pars Intermedia Dysfunction. Vet Sci 2025 Aug 20;12(8).
- Potier JF, Louzier V. Evaluation of stress markers in horses during hippotherapy sessions in comparison to being ridden by beginners. Anim Welf 2023;32:e10.
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