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Home / Equine Research Bank / J Vet Intern Med / Clinical implications of using adrenocorticotropic hormone d...
Journal of veterinary internal medicine2020; 35(1); 560-570; doi: 10.1111/jvim.16017

Clinical implications of using adrenocorticotropic hormone diagnostic cutoffs or reference intervals to diagnose pituitary pars intermedia dysfunction in mature horses.

Abstract: Diagnosis of pituitary pars intermedia dysfunction (PPID) is problematic because of large variations in ACTH concentrations. Objective: Compare the test characteristics of baseline and post-thyrotropin-releasing hormone (TRH) stimulation plasma ACTH concentrations in horses using diagnostic cutoff values (DCOVs) and reference intervals (RIs) and determine the clinical consequences of using each method. Methods: One hundred six mature horses: 72 control cases and 34 PPID cases. Methods: Prospective case-controlled study. Horses underwent monthly TRH stimulation tests. Diagnostic cutoff values were determined monthly by receiver operating characteristic curves using the Youden index. Reference intervals were determined monthly by a robust method. For each case age, sex and body condition score (BCS) were recorded. Results: Baseline ACTH concentrations varied by month (P < .001) with significant "month × age" (P = .003), "month × sex" (P = .003), and "month × BCS" (P = .007) effects. Baseline ACTH concentrations were accurate to diagnose PPID (0.91 ± 0.06) with DCOVs increasing the test sensitivity (0.61 ± 0.21 to 0.87 ± 0.05, P = .002) and RI increasing test specificity (0.85 ± 0.12 to 0.98 ± 0.01, P = .01). Thyrotropin-releasing hormone stimulation improved test accuracy (0.91 ± 0.06 to 0.97 ± 0.03, P = .004). Conclusions: ACTH concentrations follow a circannual rhythm and vary with physiological factors. As using DCOVs increases the ability to detect mild cases and using RI decreases the risk of unnecessary treatments, ACTH concentrations should be interpreted within a specific clinical context. The TRH stimulation test improves the diagnosis of PPID.
© 2020 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC. on behalf of the American College of Veterinary Internal Medicine.
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Publication Date: 2020-12-24 PubMed ID: 33368633PubMed Central: PMC7848300DOI: 10.1111/jvim.16017Google 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.

The research article explores ways to improve the diagnosis of Pituitary Pars Intermedia Dysfunction (PPID) in horses through the testing of plasma ACTH (Adrenocorticotropic Hormone) concentrations, taking into account monthly variations and the effects of age, sex, and body condition.

Objective and Methodology

Researchers aimed to compare the effectiveness of utilizing two diagnostic methods: Diagnostic Cutoff Values (DCOVs) and Reference Intervals (RIs), over monthly intervals. They also sought to understand the implications of using both methods in a clinical setting, analyzing how each would affect PPID diagnosis.

The study involved 106 mature horses divided into two groups, a control group of 72 horses and a group of 34 PPID-affected horses. By performing monthly Thyrotropin-Releasing Hormone (TRH) stimulation tests, researchers could track changes in ACTH concentrations. For data analysis, they used the Youden index in Receiver Operating Characteristic curves to determine DCOVs and a robust method for RIs.

Results

An emergent trend indicated that baseline ACTH concentrations varied significantly from month to month, with notable interaction effects relation to:

  • Month and age
  • Month and sex
  • Month and body condition score (BCS)

In terms of diagnostic efficiency, baseline ACTH concentrations were found to be a reliable indicator for diagnosing PPID. Using DCOVs, test sensitivity improved considerably, which means the ability of the test to accurately identify PPID-affected horses increased. Applying RIs, on the other hand, enhanced the test’s ability to correctly identify horses without PPID, thereby reducing the possibility of unnecessary treatments.

Amplifying the effects, the use of TRH stimulation resulted in a substantial improvement in test accuracy, further validating its application in diagnosing PPID.

Conclusions

The study concluded that diagnosing PPID in horses using ACTH concentrations must take into account various factors, such as the month of testing and horse-specific characteristics, including age, sex, and body condition. Further, the choice between DCOVs and RIs should be based on the specific clinical context, as both methods have their respective benefits: DCOVs are more suited for detecting mild cases, while RIs help avoid unnecessary treatments. The TRH stimulation test was recommended for its ability to enhance diagnostic accuracy.

Cite This Article

APA
Horn R, Stewart AJ, Jackson KV, Dryburgh EL, Medina-Torres CE, Bertin FR. (2020). Clinical implications of using adrenocorticotropic hormone diagnostic cutoffs or reference intervals to diagnose pituitary pars intermedia dysfunction in mature horses. J Vet Intern Med, 35(1), 560-570. https://doi.org/10.1111/jvim.16017

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 35
Issue: 1
Pages: 560-570

Researcher Affiliations

Horn, Remona
  • School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Stewart, Allison J
  • School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Jackson, Karen V
  • School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
Dryburgh, Elizabeth L
  • Boehringer Ingelheim Pty Ltd, North Ryde, New South Wales, Australia.
Medina-Torres, Carlos E
  • School of Veterinary Science, 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
  • Prospective Studies
  • Thyrotropin-Releasing Hormone

Grant Funding

  • Boehringer Ingelheim Pty Ltd
  • The University of Queensland

Conflict of Interest Statement

Elizabeth L. Dryburgh is employed by Boehringer‐Ingelheim Pty Ltd and François‐Rene Bertin and Allison J. Stewart have consulted for Boehringer‐Ingelheim Pty Ltd.

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Citations

This article has been cited 8 times.
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  2. 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).
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  3. Kirkwood NC, Hughes KJ, Stewart AJ. Pituitary Pars Intermedia Dysfunction (PPID) in Horses.. Vet Sci 2022 Oct 10;9(10).
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