Postnatal changes in total and free thyroxine and triiodothyronine in foal serum.
Abstract: Total tyhroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT3) and free triiodothyronine (FT3) concentrations in foal umbilical cord blood were respectively 14, 5 7 and 3 times the concentrations of these hormones in adult horse blood. The TT4 levels in foals declined rapidly to reach adult concentrations by Day 16 and FT4 levels declined steadily during the first 3 months of life. Foal TT3 levels rose during the first 10 hr after birth and thereafter declined, although they were still X2-5 higher than adult levels at 3 months of age. Levels of FT3 similarly increased after birth becoming X8 higher than adult levels at 3 days of age. They declined after this time but were still twice the normal adult levels at 3 months of age. Associated with these age changes were an increase in the free hormone percentage and a decrease in binding protein concentration. The very high levels of thyroid hormones in newborn foals may be responsible for their extremely high thermogenic capacity and rapid pre- and post-natal rates of growth, especially of the musculo-skeletal and nervous systems.
Publication Date: 1975-10-01 PubMed ID: 1060870
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- 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.
The research article discusses the postnatal changes in thyroid hormone levels in foals (baby horses). It highlights how these hormone levels are significantly higher in newborn foals compared to adult horses, and how these levels gradually decrease over time, possibly influencing the rapid growth and high thermogenic capacity observed in foals.
Examination of Thyroid Hormone Levels
- The study focused on the concentration levels of total thyroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT3) and free triiodothyronine (FT3) in foal’s umbilical cord blood.
- These hormone concentrations were found to be significantly higher in foals as compared to adult horses. Specifically, TT4 levels were 14 times, FT4 levels 5 times, TT3 levels 7 times, and FT3 levels 3 times higher in foals at birth.
Changes in Thyroid Hormone Levels Post Birth
- Following birth, the levels of these hormones in foals rapidly changed to resemble that of adult horses.
- TT4 levels saw a rapid decline, reaching levels similar to adult horses by the 16th day after birth.
- FT4 levels, on the other hand, saw a gradual decrease over the first 3 months.
- TT3 levels initially rose in the first 10 hours after birth, thereafter showing a decline, whilst still remaining 2.5 times higher than adult levels at 3 months old.
- FT3 levels exhibited a similar trend, increasing post birth and reaching 8 times the adult level at 3 days old. Although these levels declined over time, they were still twice as high as adult levels at 3 months old.
Correlation Between Thyroid Hormones and Postnatal Development
- The research suggests that these high thyroid hormone levels in newborn foals correlate with their exceptionally rapid pre- and post-natal growth, especially pertaining to their musculoskeletal and nervous systems.
- The high thyroid hormone levels could also be responsible for the neonatal foal’s significant thermogenic capacity, i.e., their ability to produce heat, which is vital for maintaining body temperature.
Cite This Article
APA
Irvine CH, Evans MJ.
(1975).
Postnatal changes in total and free thyroxine and triiodothyronine in foal serum.
J Reprod Fertil Suppl(23), 709-715.
Publication
Researcher Affiliations
MeSH Terms
- Age Factors
- Animals
- Animals, Newborn / growth & development
- Fetal Blood / analysis
- Horses / blood
- Thyroxine / blood
- Triiodothyronine / blood
Citations
This article has been cited 10 times.- Robles M, Nouveau E, Gautier C, Mendoza L, Dubois C, Dahirel M, Lagofun B, Aubrière MC, Lejeune JP, Caudron I, Guenon I, Viguié C, Wimel L, Bouraima-Lelong H, Serteyn D, Couturier-Tarrade A, Chavatte-Palmer P. Maternal obesity increases insulin resistance, low-grade inflammation and osteochondrosis lesions in foals and yearlings until 18 months of age. PLoS One 2018;13(1):e0190309.
- Peugnet P, Wimel L, Duchamp G, Sandersen C, Camous S, Guillaume D, Dahirel M, Dubois C, Jouneau L, Reigner F, Berthelot V, Chaffaux S, Tarrade A, Serteyn D, Chavatte-Palmer P. Enhanced or reduced fetal growth induced by embryo transfer into smaller or larger breeds alters post-natal growth and metabolism in pre-weaning horses. PLoS One 2014;9(7):e102044.
- Breuhaus BA. Thyroid function and dysfunction in term and premature equine neonates. J Vet Intern Med 2014 Jul-Aug;28(4):1301-9.
- McLaughlin BG, Doige CE, McLaughlin PS. Thyroid hormone levels in foals with congenital musculoskeletal lesions. Can Vet J 1986 Jul;27(7):264-7.
- McLaughlin BG, Doige CE. A study of ossification of carpal and tarsal bones in normal and hypothyroid foals. Can Vet J 1982 May;23(5):164-8.
- McLaughlin BG, Doige CE. Congenital musculosketal lesions and hyperplastic goitre in foals. Can Vet J 1981 May;22(5):130-3.
- 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).
- Pasolini MP, Auletta L, De Biase D, Vaccaro E, Del Prete C, Montano C, de Chiara M, Di Napoli E, Paciello O, Piegari G. Clinical and Pathological Features of Flexural Deformities Associated with Myopathies in Foals. Vet Sci 2025 Jun 6;12(6).
- Ishimaru M, Kume K, Murase H, Sato F, Matsui A, Ohmura H, Taya K. Effect of birth month on endocrine function in Thoroughbred foals born in Hokkaido, the northern part of Japan. J Vet Med Sci 2025 Jul 7;87(7):804-815.
- Heidkamp M, Herwig A, Singer D. Mammalian birth versus arousal from hibernation: thyroid hormones, common regulators of metabolic transition?. J Comp Physiol B 2025 Jun;195(3):277-292.
Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists
