Thyroid hormone responses to endurance exercise.
Abstract: Limited information exists about changes in circulating thyroid hormone concentrations during prolonged endurance exercise in horses. Objective: To examine the effects of prolonged exercise on serum iodothyronine concentrations in horses performing endurance exercise of varying distances. Methods: Serum concentrations of iodothyronines were measured in horses before and after completion of 40, 56, 80 and 160 km endurance rides (Study 1); daily during a 5 day, 424 km endurance ride (Study 2); and before and for 72 h after completion of a treadmill exercise test simulating a 60 km endurance ride (Study 3). Results: In Study 1, 40 and 56 km of endurance exercise had little effect on serum iodothyronine concentrations with the exception of a 10% decrease (P<0.05) in free thyroxine (FT4) concentration after the 56 km ride. In contrast, total thyroxine (T4), total triiodothyronine (T3), FT4 and free triiodothyronine (FT3) concentrations all decreased (P<0.05) after successful completion of 80 and 160 km rides, with decreases ranging from 13-31% and 47-54% for distances of 80 and 160 km, respectively. Further, pre-ride T4 concentration was lower (P<0.05) and FT3 concentration was higher (P<0.05) in horses competing 160 km as compared to horses competing over shorter distances. In Study 2, serum concentrations of T4, T3 and reverse triiodothyronine (rT3) progressively decreased (P<0.05) over the course of the multi-day ride. In Study 3, the greatest decrease (P<0.05) in all iodothyronines was observed at 12 h of recovery, ranging from 25% for FT4 to 53% for FT3, but all thyroid hormone concentrations had returned to the pre-exercise values by 24 h of recovery. Conclusions: Endurance exercise results in transient decreases in serum iodothyronine concentrations. Conclusions: These data are important to consider when thyroid gland function is assessed by measurement of serum iodothyronine concentrations in endurance horses.
Publication Date: 2007-04-04 PubMed ID: 17402388DOI: 10.1111/j.2042-3306.2006.tb05509.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research article investigates the changes in circulating thyroid hormone concentrations in horses during endurance exercise. This study found that endurance exercise results in temporary decreases in these hormone levels, affecting the assessment of the thyroid gland’s function in endurance horses.
Objective and Methods
- The objective of the study was to examine the effects of endurance exercise on the serum concentration of iodothyronines (a group of hormones created and released by the thyroid gland) in horses. This was done during endurance exercises of various distances.
- The study was carried out in three phases: the first study involved monitoring horses before and after endurance rides of 40, 56, 80, and 160 kilometers; the second study involved daily tracking during a five-day endurance ride covering a total of 424 kilometers; the third study looked at horses before and for 72 hours after a treadmill work simulating a 60-kilometer ride.
Results
- In the first study, 40 and 56-kilometer endurance rides had minimal effect on the horses’ serum iodothyronine levels except for a 10% decrease in free thyroxine (FT4) concentration after the 56-kilometer ride.
- In contrast, longer endurance rides of 80 and 160 kilometers led to significant decreases in the concentrations of total thyroxine (T4), total triiodothyronine (T3), FT4, and free triiodothyronine (FT3). The decrease ranged from 13% to 31% after 80 kilometers and 47% to 54% after 160 kilometers.
- Before 160-kilometer rides, horses had lower T4 concentrations and higher FT3 concentrations than horses competing over shorter distances.
- The second study found that T4, T3, and reverse triiodothyronine (rT3) levels progressively decreased over the course of a multi-day ride.
- In the third study, the most pronounced decrease in all iodothyronines was observed 12 hours into recovery, decreasing from 25% for FT4 to 53% for FT3. However, all thyroid hormone concentrations had returned to their pre-exercise values by 24 hours of recovery.
Conclusion
- This study concluded that endurance exercise causes temporary decreases in the concentration of thyroid hormones (iodothyronines) in the serum of horses.
- These findings are crucial when the thyroid gland’s function is assessed by measuring serum iodothyronine concentrations in endurance horses.
Cite This Article
APA
Graves EA, Schott HC, Marteniuk JV, Refsal KR, Nachreiner RF.
(2007).
Thyroid hormone responses to endurance exercise.
Equine Vet J Suppl(36), 32-36.
https://doi.org/10.1111/j.2042-3306.2006.tb05509.x Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48824-1314, USA.
MeSH Terms
- Animals
- Female
- Horses / blood
- Horses / physiology
- Male
- Physical Conditioning, Animal / physiology
- Physical Endurance / physiology
- Sports
- Thyroid Gland / physiology
- Thyroid Hormones / blood
- Thyroxine / blood
- Time Factors
- Triiodothyronine / blood
Citations
This article has been cited 2 times.- Ferlazzo A, Cravana C, Fazio E, Medica P. The different hormonal system during exercise stress coping in horses. Vet World 2020 May;13(5):847-859.
- Tangyuenyong S, Nambo Y, Nagaoka K, Tanaka T, Watanabe G. Sensitive radioimmunoassay of total thyroxine (T4) in horses using a simple extraction method. J Vet Med Sci 2017 Jul 28;79(7):1294-1300.
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