Thyroid hormones may influence the slow component of V̇o2 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 V̇O2 slow component (ΔV̇O2) 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 V̇O2max (or ∼400W). Plasma concentrations of T3 and T4 were inversely correlated (p<0.05) with ΔV̇O2 (r=-0.72 and r=-0.66, respectively), suggesting, at least partly, and association between thyroid basal function and the V̇O2 slow component of euthyroid elite endurance athletes during constant-load intense exercise.