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


CONCLUSIONS
In conclusion, 3 weeks of competition provokes changes in basal thyroid hormone concentrations in professional road cyclists.
Chicharro
J L
JL
Departamento de Enfermería, Universidad Complutense de Madrid, Spain. jlchicharro@enf.ucm.es
Hoyos
J
J
Bandrés
F
F
Terrados
N
N
Fernández
B
B
Lucía
A
A
D000328:Adult; D001642:Bicycling; D001835:Body Weight; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008297:Male; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood*; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood*
D006454:Hemoglobins; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine