Thyroid hormone levels during a 3-week professional road cycling competition
Related Experiment Video
Updated: Oct 2, 2026

A Versatile, Behavioral Method to Investigate Thyroid Hormone Effects on Cerebellar Function
Published on: October 6, 2023
J L Chicharro1, J Hoyos, F Bandrés
1Departamento de Enfermería, Universidad Complutense de Madrid, Spain. jlchicharro@enf.ucm.es
Aims:
The aim of this investigation was to examine the thyroid hormone levels of professional cyclists during a 3-week stage competition (Vuelta a España 1998).
Methods:
The study population was made up of 16 male cyclists from two world-leading professional teams. Four blood samples were drawn (between 07:00 and 09:00 a.m.) from each participant before and at the end of the 1st, 2nd and 3rd weeks of competition. 3,5,3'(-Triiodothyronine (T(3)), free T(3) (FT(3)), thyroxine (T(4)), free T(4) (FT(4)) and thyroid-stimulating hormone (TSH) were determined in each blood sample by radioimmunoassay.
Results:
Serum T(4), FT(4) and FT(3) levels showed a significant increase (p < 0.05) by the last week of competition while concentrations of TSH and T(3) remained unchanged.
Conclusion:
In conclusion, 3 weeks of competition provokes changes in basal thyroid hormone concentrations in professional road cyclists.
Related Concept Videos
Hyperthyroidism I: Introduction
Hyperthyroidism II: Pathophysiology
Synthesis and Regulation of Thyroid Hormones
Upon reaching the thyroid gland, TSH stimulates the follicular cells' active uptake of iodide ions from the blood. The ions diffuse to the apical surface of the cells and are oxidized to iodine. The iodine is then...
Graves Disease II: Pathophysiology
Goiter
Functions of Thyroid Hormones
TH is indispensable for the normal development and maturation of the skeletal, muscular, and nervous systems during fetal and childhood growth. It facilitates bone mineral turnover and regulates protein synthesis in developing tissues, contributing significantly to overall growth and...