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Thyroid hormone levels during a 3-week professional road cycling competition
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.