Strenuous, Fatiguing Exercise: Relationship of Cortisol to Circulating Thyroid Hormones

Abstract

he purposes of this study were to determine how strenuous, fatiguing running exercise affects: 1) selective thyroid hormones, and 2) the relationship of glucocorticoid responses to such exercise with thyroid hormones. Materials and Methods: Well-trained subjects (n=12) performed a treadmill run at individual ventilatory threshold (74±8% of maximal aerobic capacity) until volitional fatigue (68.3±12.3 min).Blood samples were taken before exercise as a resting baseline (BO), at fatigue (FG), 90-minutes into recovery (90mR), and 24-hours into recovery (24hR). Blood was analyzed for free T3 (fT3), free T4 (fT4), thyroid-stimulating hormone (TSH),and cortisol. Results: Significant increases in fT3 and TSH concentrations between BO and FG (fT3= 1.70 pglmL vs. 2.08 pglmL; TSH=1.69 pIU/mL vs. 2.43 pIU/mL, p tively; p