Thyrotropin and free thyroid hormones in athletes during and after ultra-endurance sport performances

Hormone concentrations can change during exercise, particularly during long and strenuous performances. We studied thyrotropin (TSH) and free thyroid hormones (fT3 and fT4) in three groups of athletes performing endurance races (mountain marathon, water skiing and 24 hours of speed skating), Statistical differences in TSH values between blood drawings were found in ice skaters, whereas non-significant differences were found for fT3 and fT4, Mountain marathoners and water skiers did not show significant differences for thyroid hormones with the exception of fT3, which increased after the mountain race. Our study shows that ultralong exercise did not induce clinically consistent TSH, fT3 and fT4 variations in well trained athletes performing endurance and ultraendurance exercises. The observed variations are mainly linked to the different increases in metabolic demands characterizing each competition, while stress and environmental conditions seem to cause only minor effects.