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Home / Equine Research Bank / J Vet Intern Med / Repeatability of a thyrotropin-releasing hormone stimulation...
Journal of veterinary internal medicine2021; 35(6); 2885-2890; doi: 10.1111/jvim.16281

Repeatability of a thyrotropin-releasing hormone stimulation test for diagnosis of pituitary pars intermedia dysfunction in mature horses.

Abstract: Pituitary pars intermedia dysfunction (PPID) is a common endocrinopathy of horses diagnosed with a thyrotropin-releasing hormone (TRH) stimulation test. Objective: Describe the repeatability of TRH stimulation in horses with and without PPID in winter and autumn. Methods: Twenty adult horses; 6 controls and 6 with PPID tested in autumn, 8 controls and 6 with PPID tested in winter with 3 controls and 3 with PPID tested in both seasons. Methods: Thyrotropin-releasing hormone stimulation was performed on 2 consecutive occasions, 1 week before and 1 week after the winter solstice and the autumn equinox. Blood was collected before and 30 minutes after IV injection of 1 mg of TRH. ACTH concentration was determined by a chemiluminescent assay. Repeatability and test-retest reliability were assessed by repeated measures analysis of variance, intraclass correlation coefficient and within-horse coefficients of variation (CV). Bland-Altman plots were generated to visualize agreement between repetitions. Results: In winter, no week effect was detected on the results of the TRH simulation and the test had an excellent test-retest reliability. In autumn, after-TRH ACTH concentrations were significantly lower on week 2 (P = .02) and the test only had a good test-retest reliability. There were significantly larger within-horse CV during autumn (P = .04) and after TRH stimulation (P = .04). There were 2 misclassifications in winter and 4 in autumn. Conclusions: The TRH stimulation test was repeatable when performed 2 weeks apart in winter; however, in autumn, more variability in after-TRH ACTH concentrations resulted in decreased repeatability.
© 2021 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.
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Publication Date: 2021-10-13 PubMed ID: 34642962PubMed Central: PMC8692209DOI: 10.1111/jvim.16281Google Scholar: Lookup
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  • Journal Article

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.

The research article explores the reliability of the thyrotropin-releasing hormone (TRH) stimulation test for diagnosing Pituitary pars intermedia dysfunction (PPID) in horses. The results indicate that the test was more repeatable and reliable when performed during the winter compared to the autumn season.

Objective and Methodology

  • The main aim of this study was to observe the repeatability of the TRH stimulation test for diagnosing PPID, a common endocrine disorder in horses, during different seasons (autumn and winter).
  • The experiment involved twenty adult horses divided into two categories: controls (healthy horses) and those with PPID. Each category was further split according to the season of testing.
  • The TRH stimulation test was performed on two separate occasions – one week before and one week after the winter solstice and the autumn equinox. Blood samples were collected before and 30 minutes after administering a 1 mg IV injection of TRH.
  • The concentrations of adrenocorticotropic hormone (ACTH), a hormone released in response to TRH stimulation, were determined through a chemiluminescent assay.
  • The repeatability and test-retest reliability of the TRH stimulation test were assessed through repeated measures analysis of variance, intraclass correlation coefficient, and within-horse coefficients of variation (CV).

Results

  • In winter, the TRH stimulation test showed no week effect, indicating excellent test-retest reliability.
  • However, in autumn, the ACTH concentrations post-TRH stimulation were significantly lower during the second week, leading to only good test-retest reliability.
  • There was a larger within-horse CV noted during the autumn as well as post-TRH stimulation, indicating more variability.
  • As far as the misclassification of the test results is concerned, it was higher in autumn (4) compared to winter (2).

Conclusions

  • Based on the results, the research concluded that the repeatability of the TRH stimulation test was higher when performed during the winter.
  • The increased variability in ACTH concentrations post-TRH stimulation in autumn led to decreased repeatability in this season.

Cite This Article

APA
Kam YN, McKenzie K, Coyle M, Bertin FR. (2021). Repeatability of a thyrotropin-releasing hormone stimulation test for diagnosis of pituitary pars intermedia dysfunction in mature horses. J Vet Intern Med, 35(6), 2885-2890. https://doi.org/10.1111/jvim.16281

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 35
Issue: 6
Pages: 2885-2890

Researcher Affiliations

Kam, Yan Ning
  • School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
McKenzie, Kelly
  • School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Coyle, Mitchell
  • Office of the Director of Gatton Campus, The University of Queensland, Gatton, Queensland, Australia.
Bertin, François-René
  • School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.

MeSH Terms

  • Adrenocorticotropic Hormone / metabolism
  • Animals
  • Horse Diseases / diagnosis
  • Horses
  • Pituitary Diseases / diagnosis
  • Pituitary Diseases / veterinary
  • Pituitary Gland, Intermediate
  • Reproducibility of Results
  • Thyrotropin-Releasing Hormone

Grant Funding

  • John and Mary Kibble Trust Fund

Conflict of Interest Statement

Authors declare no conflict of interest.

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Citations

This article has been cited 3 times.
  1. 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).
    doi: 10.3390/vetsci9100572pubmed: 36288186google scholar: lookup
  2. Kirkwood NC, Hughes KJ, Stewart AJ. Pituitary Pars Intermedia Dysfunction (PPID) in Horses.. Vet Sci 2022 Oct 10;9(10).
    doi: 10.3390/vetsci9100556pubmed: 36288169google scholar: lookup
  3. 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.
    doi: 10.1111/jvim.16362pubmed: 35049089google scholar: lookup
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