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The British veterinary journal1992; 148(1); 71-80; doi: 10.1016/0007-1935(92)90069-D

Equine thyroid function tests: a preliminary investigation.

Abstract: A similar and significant (P less than 0.001) increase in plasma thyroxine (T4) concentration was seen in seven clinically normal thoroughbred horses 2 h after the intravenous administration of either 2.5 iu or 5 iu of thyroid stimulating hormone (TSH) with a peak response around 4 h after administration. The intravenous administration of 0.2, 0.5 or 1 mg thyrotrophin releasing hormone (TRH) resulted in a significant (P less than 0.01) increase in T4 concentration in three groups of animals; six thoroughbreds in full work, five thoroughbreds at rest and four ponies at rest. The peak response was recorded at 3 or 4 h after administration. A significant difference between the groups in the degree of response to TRH was only found between the thoroughbreds in work and those at rest with 1 mg TRH (P less than 0.05). When two additional ponies were investigated in a similar way, a reduced response to TRH was observed: a pregnant mare had a similar response to 5 iu TSH as the thoroughbreds; the other pony also showed a lowered response to TSH. In a group of 2- or 3-year-old thoroughbreds in training no difference in the T4 response 4 h after intravenous administration of 0.5 mg TRH could be determined, according to the month, age, sex or work intensity. Although resting T4 concentrations did not differ significantly between animals believed to be suffering from the equine rhabdomyolysis syndrome (ERS) and those suffering from a variety of other conditions, some ERS sufferers may have a lowered response to TRH.
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Publication Date: 1992-01-01 PubMed ID: 1551018DOI: 10.1016/0007-1935(92)90069-DGoogle 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.

This study explores the changes observed in thyroid function in thoroughbred horses after administering thyroid stimulating hormones. Differences in response were measured among horses in various states of activity, months, age, sex, and health conditions.

Methodology and General Findings

  • The researchers conducted thyroid function tests on groups of thoroughbred horses and ponies. Tests involved the intravenous administration of thyroid stimulating hormone (TSH) and thyrotrophin releasing hormone (TRH).
  • Significant increases in plasma thyroxine (T4) concentration were observed in seven horses, approximately 2 to 4 hours after injection of either 2.5 iu or 5 iu of TSH.
  • All three groups of animals exposed to TRH (thoroughbreds in full work, thoroughbreds at rest, and ponies at rest) exhibited a significant increase in T4 concentration. The peak response was marked at around 3 to 4 hours post-injection.

Specific Findings and Observations

  • Among the groups exposed to TRH, a significant difference in the degree of T4 response was only observed between thoroughbreds in work and those at rest after they were given 1 mg TRH.
  • Two additional ponies exhibited a reduced response to TRH. A pregnant mare mirrored the T4 response of the thoroughbreds to 5 iu TSH, while the other pony showed a decreased response to TSH.

Further Observations and Conclusion

  • In a cohort of young thoroughbreds in training, researchers found no difference in T4 response following injection of 0.5 mg TRH, regardless of the month, age, sex, or work intensity.
  • Whilst the resting T4 concentrations revealed no marked disparities between horses thought to be suffering from equine rhabdomyolysis syndrome (ERS) and those with other health conditions, some ERS afflicted horses may exhibit a reduced response to TRH.

In conclusion, this preliminary investigation offers insights into differences in thyroid function response in thoroughbred horses under varying conditions. The study also hints at possible alterations in thyroid function in horses suffering from ERS. However, these observations warrant further research to form solid conclusions.

Cite This Article

APA
Harris P, Marlin D, Gray J. (1992). Equine thyroid function tests: a preliminary investigation. Br Vet J, 148(1), 71-80. https://doi.org/10.1016/0007-1935(92)90069-D

Publication

The British veterinary journal
ISSN: 0007-1935
NlmUniqueID: 0372554
Country: England
Language: English
Volume: 148
Issue: 1
Pages: 71-80

Researcher Affiliations

Harris, P
  • Animal Health Trust, Newmarket, Suffolk.
Marlin, D
    Gray, J

      MeSH Terms

      • Animals
      • Female
      • Horse Diseases / diagnosis
      • Horses / physiology
      • Male
      • Rhabdomyolysis / diagnosis
      • Rhabdomyolysis / veterinary
      • Thyroid Function Tests / veterinary
      • Thyroid Gland / physiology
      • Thyrotropin
      • Thyrotropin-Releasing Hormone
      • Thyroxine / blood

      Citations

      This article has been cited 2 times.
      1. 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
      2. 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
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