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Home / Equine Research Bank / J Vet Intern Med / Nonthyroidal illness syndrome in adult horses.
Journal of veterinary internal medicine2014; 28(2); 609-617; doi: 10.1111/jvim.12274

Nonthyroidal illness syndrome in adult horses.

Abstract: This study was performed to determine whether sick horses have thyroid hormone (TH) alterations similar to those observed in nonthyroidal illness syndrome in other species. Objective: Horses suffering from systemic diseases have decreased THs and inappropriately low thyroid-stimulating hormone (TSH). Methods: Seventy-one clinically normal horses; 380 hospitalized horses. Methods: Total thyroxine (TT4), free thyroxine by equilibrium dialysis (fT4D), total triiodothyronine (TT3), free triiodothyronine (fT3), and TSH were measured in normal and hospitalized horses. Disease severity was categorized as mild, moderate, or severe by both subjective and objective criteria. Results: Negative correlations existed between all THs, except TSH, and objective illness severity scores. These scores also increased with each subjective disease severity category. TT3 and fT3 were decreased with mild disease. TT3 progressively decreased more with moderate and severe disease. TT4 and fT4D remained normal with mild disease, but decreased progressively with disease severity. TSH increased with mild disease, but remained normal with moderate or severe disease. Horses that died or were euthanized had lower concentrations of all THs, except TSH, when compared with those that lived. In horses that received >3 doses of NSAIDs, corticosteroids, or heparin compared to 0-3 doses, TT3 and TT4 were decreased, whereas fT4D and TSH remained normal. There were minimal TH changes in horses that were not eating. Conclusions: Thyroid hormones decrease in horses with systemic disease. TT3 decreases first, followed by TT4 and fT4D. TSH fails to increase proportionally to the changes in THs, indicating hypothalamic-pituitary axis dysregulation. NSAIDs, corticosteroids, heparin, and fasting have less effect on THs compared with disease severity.
Copyright © 2014 by the American College of Veterinary Internal Medicine.
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Publication Date: 2014-01-13 PubMed ID: 24417524PubMed Central: PMC4857970DOI: 10.1111/jvim.12274Google 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 study examines the occurrence of Nonthyroidal illness syndrome (an alteration in thyroid hormone levels) in adult horses suffering from systemic diseases. The research’s main findings include the discovery that a decrease in thyroid hormones correlates with disease severity, suggesting a dysregulation in the hypothalamic-pituitary axis in these horses.

Objective

  • The main goal of this study was to identify if horses with systemic diseases exhibit alterations in their thyroid hormones, similar to Nonthyroidal Illness Syndrome seen in other species.

Methods

  • The study involved 71 clinically normal horses and 380 hospitalized horses suffering from systemic diseases.
  • Through the study, the total thyroxine (TT4), free thyroxine by equilibrium dialysis (fT4D), total triiodothyronine (TT3), free triiodothyronine (fT3), and thyroid-stimulating hormone (TSH) levels were measured in both normal and hospitalized horses.
  • Disease severity was subjectively and objectively categorized as mild, moderate, or severe.

Results

  • Findings suggest that negative correlations exist between all thyroid hormones, barring TSH, and the objective illness severity scores. This means as the illness severity grew, the thyroid hormone levels decreased.
  • TT3 and fT3 were found to decrease with mild disease and progressively drop with the severity of the disease.
  • TT4 and fT4D remained normal during mild disease but decreased progressively with the severity.
  • TSH, however, increased with mild disease but remained normal with moderate or severe disease.
  • Horses that either died or were euthanized demonstrated lower concentrations of all thyroid hormones except for TSH compared to those that survived.
  • Finally, horses that received more than three doses of NSAIDs, corticosteroids, or heparin showed decreased levels of TT3 and TT4, while fT4D and TSH remained normal.

Conclusions

  • Overall, the study concludes that systemic diseases in horses lead to a decrease in thyroid hormones, with TT3 decreasing first, followed by TT4 and fT4D.
  • The study also revealed that, unlike the thyroid hormones, TSH doesn’t increase proportionally, indicating a dysregulation in the hypothalamic-pituitary axis.
  • It was also noted that NSAIDs, corticosteroids, heparin, and fasting seem to have less effect on thyroid hormone levels when compared with disease severity.

Cite This Article

APA
Hilderbran AC, Breuhaus BA, Refsal KR. (2014). Nonthyroidal illness syndrome in adult horses. J Vet Intern Med, 28(2), 609-617. https://doi.org/10.1111/jvim.12274

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 28
Issue: 2
Pages: 609-617

Researcher Affiliations

Hilderbran, A C
  • Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC.
Breuhaus, B A
    Refsal, K R

      MeSH Terms

      • Animals
      • Case-Control Studies
      • Female
      • Horse Diseases / blood
      • Horse Diseases / physiopathology
      • Horses
      • Male
      • Severity of Illness Index
      • Syndrome
      • Thyroid Gland / physiopathology
      • Thyroid Hormones / blood
      • Thyroid Hormones / physiology
      • Thyrotropin / blood
      • Thyrotropin / physiology
      • Thyroxine / blood
      • Thyroxine / physiology
      • Triiodothyronine / blood
      • Triiodothyronine / physiology

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      Citations

      This article has been cited 6 times.
      1. Stoeckle SD, Stage HJ, Gehlen H. Thyroid Disease in Horses-Retrospective Case Series on Patients Examined for Thyroid Disease in an Equine University Clinic (2009-2024). Vet Sci 2025 Nov 27;12(12).
        doi: 10.3390/vetsci12121127pubmed: 41472107google scholar: lookup
      2. Moss A, Leise B, Hackett E. Stress response as a contributing factor in horses with laminitis. J Vet Sci 2023 Mar;24(2):e33.
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      3. Pasternak JA, MacPhee DJ, Lunney JK, Rowland RRR, Dyck MK, Fortin F, Dekkers JCM, Plastow GS, Harding JCS. Thyroid hormone suppression in feeder pigs following polymicrobial or porcine reproductive and respiratory syndrome virus-2 challenge. J Anim Sci 2021 Nov 1;99(11).
        doi: 10.1093/jas/skab325pubmed: 34734242google scholar: lookup
      4. Gehlen H, Jaburg N, Merle R, Winter J. Can Endocrine Dysfunction Be Reliably Tested in Aged Horses That Are Experiencing Pain?. Animals (Basel) 2020 Aug 14;10(8).
        doi: 10.3390/ani10081426pubmed: 32824027google scholar: lookup
      5. Costello J, Firshman AM, Brown JC, Maher M, Tadros EM. Response to thyrotropin-releasing hormone (TRH) in a horse with hyperthyroidism associated with a functional thyroid adenoma. Can Vet J 2019 Nov;60(11):1189-1193.
        pubmed: 31692666
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        doi: 10.1111/jvim.12382pubmed: 24934827google scholar: lookup
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