Thyroid-stimulating hormone in adult euthyroid and hypothyroid horses.
Abstract: The purpose of this study was to validate a thyroid-stimulating hormone (TSH) assay in a model of equine hypothyroidism. Thyrotropin-releasing hormone (TRH) stimulation tests were performed in 12 healthy adult mares and geldings, aged 4 to greater than 20 years. before and during administration of the antithyroid drug propylthiouracil (PTU) for 6 weeks. Serum concentrations of equine TSH, total and free thyroxine (T4), and total and free triiodothyronine (T3) were measured. Before PTU administration, mean +/- standard deviation baseline concentrations of TSH were 0.40 +/- 0.29 ng/mL. TSH increased in response to TRH, reaching a peak concentration of 0.78 +/- 0.28 ng/mL at 45 minutes. Total and free T4 increased from 12.9 +/- 5.6 nmol/L and 12.2 +/- 3.5 pmol/L to 36.8 +/- 11.4 nmol/L and 23.1 +/- 5.9 pmol/L, respectively, peaking at 4-6 hours. Total and free T3 increased from 0.99 +/- 0.51 nmol/L and 2.07 +/- 1.14 pmol/L to 2.23 +/- 0.60 nmol/l and 5.78 +/- 1.94 pmol/L, respectively, peaking at 2-4 hours. Weekly measurements of baseline TSH and thyroid hormones during PTU administration showed that total and free T, concentrations fell abruptly and remained low throughout PTU administration. Total and free T4 concentrations did not decrease dramatically until weeks 5 and 4 of PTU administration, respectively. A steady increase in TSH concentration occurred throughout PTU administration, with TSH becoming markedly increased by weeks 5 and 6 (1.46 +/- 0.94 ng/mL at 6 weeks). During weeks 5 and 6 of PTU administration, TSH response to TRH was exaggerated, and thyroid hormone response was blunted. Results of this study show that measurement of equine TSH in conjunction with thyroid hormone measurement differentiated normal and hypothyroid horses in this model of equine hypothyroidism.
Publication Date: 2002-02-02 PubMed ID: 11822799DOI: 10.1892/0891-6640(2002)016<0109:tshiae>2.3.co;2Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Validation Study
Summary
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The research article is based on a study conducted to validate an assay to measure thyroid-stimulating hormone (TSH) in horses, and its value in distinguishing between euthyroid (normal functioning thyroid) and hypothyroid (underactive thyroid) horses.
Objective of the Research
The main goal of this study was to test the value and accuracy of a thyroid-stimulating hormone (TSH) assay in a model of equine hypothyroidism. Hypothyroidism is a disorder that occurs when the thyroid gland in the horse doesn’t produce enough thyroid hormone.
Methodology
- Twelve adult healthy horses, including both mares and geldings aged 4 to more than 20 years, were subjects in this study.
- Thyrotropin-releasing hormone (TRH) stimulation tests were performed before and during the 6-week administration of propylthiouracil (PTU), an antithyroid drug.
- The study monitored TSH, total and free thyroxine (T4), and total and free triiodothyronine (T3), important hormones in the metabolism and growth of the horse.
Results
- Before PTU administration, the baseline TSH concentration was relatively low.
- With TRH administration, TSH, total and free T4, and T3 levels increased, with peak concentrations at various times.
- During PTU administration, total and free TSH concentrations fell significantly and remained low.
- Total and free T4 concentrations showed noticeable decreases during the 4th and 5th weeks of PTU administration.
- There was a consistent increase in TSH concentration throughout the PTU administration, with a significant increase seen by the 5th and 6th week.
- The TSH response to TRH was exaggerated, and hormone response was blunted in weeks 5 and 6 of PTU administration.
Conclusion
The results of the study demonstrated that measuring equine TSH in combination with thyroid hormone measurements could effectively differentiate between normal and hypothyroid horses. This suggests the potential value of the TSH assay as a diagnostic tool in equine medicine.
Cite This Article
APA
Breuhaus BA.
(2002).
Thyroid-stimulating hormone in adult euthyroid and hypothyroid horses.
J Vet Intern Med, 16(1), 109-115.
https://doi.org/10.1892/0891-6640(2002)016<0109:tshiae>2.3.co;2 Publication
Researcher Affiliations
- North Carolina State University, College of Veterinary Medicine, Raleigh 27606, USA. betta_breuhaus@ncsu.edu
MeSH Terms
- Animals
- Disease Models, Animal
- Female
- Horse Diseases / chemically induced
- Horse Diseases / diagnosis
- Horses
- Hypothyroidism / chemically induced
- Hypothyroidism / diagnosis
- Hypothyroidism / veterinary
- Male
- Predictive Value of Tests
- Propylthiouracil
- Reproducibility of Results
- Sensitivity and Specificity
- Thyrotropin / blood
- Thyrotropin / drug effects
- Thyrotropin-Releasing Hormone / pharmacology
- Thyroxine / blood
- Thyroxine / drug effects
- Triiodothyronine / blood
- Triiodothyronine / drug effects
Citations
This article has been cited 5 times.- Kirkwood NC, Hughes KJ, Stewart AJ. Pituitary Pars Intermedia Dysfunction (PPID) in Horses.. Vet Sci 2022 Oct 10;9(10).
- 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.
- Shao SS, Zhao YF, Song YF, Xu C, Yang JM, Xuan SM, Yan HL, Yu CX, Zhao M, Xu J, Zhao JJ. Dietary high-fat lard intake induces thyroid dysfunction and abnormal morphology in rats.. Acta Pharmacol Sin 2014 Nov;35(11):1411-20.
- Breuhaus BA. Thyroid function and dysfunction in term and premature equine neonates.. J Vet Intern Med 2014 Jul-Aug;28(4):1301-9.
- Hilderbran AC, Breuhaus BA, Refsal KR. Nonthyroidal illness syndrome in adult horses.. J Vet Intern Med 2014 Mar-Apr;28(2):609-17.
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