Thyroid Hormones May Influence the Slow Component of V˙O₂ in Professional Cyclists

Abstract

We analyzed the relationship between the plasma concentrations of several hormones (testosterone [T], follicle-stimulating [FSH] and luteinizing hormone [LH], cortisol [C], 3,5,3′-triiodothyronine [T₃], thyroxine [T₄], and thyrotrophin [TSH]) and the magnitude of the V˙O₂ slow component (δV˙O₂) in a group of nine professional road cyclists (26±2 years). The resting levels of the aforementioned hormones were determined before the subjects performed a 20-min cycle ergometer test at ~80% of V˙O_{2 max} (or ~400 W). Plasma concentrations of T₃ and T₄ were inversely correlated (p<0.05) with δV˙O₂ (r=−0.72 and r=−0.66, respectively), suggesting, at least partly, and association between thyroid basal function and the V˙O₂ slow component of euthyroid elite endurance athletes during constant-load intense exercise.