title: Thyroid hormone levels during a 3-week professional road cycling competition.
abstract: 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.
authors.affiliation: Departamento de Enfermería, Universidad Complutense de Madrid, Spain. jlchicharro@enf.ucm.es
authors.forename: J L
authors.initials: JL
authors.lastname: Chicharro
authors.forename: J
authors.initials: J
authors.lastname: Hoyos
authors.forename: F
authors.initials: F
authors.lastname: Bandrés
authors.forename: N
authors.initials: N
authors.lastname: Terrados
authors.forename: B
authors.initials: B
authors.lastname: Fernández
authors.forename: A
authors.initials: A
authors.lastname: Lucía
mesh_terms: 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*
chemical_list: D006454:Hemoglobins; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine