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

authors:

avatar AW Moore 1 , avatar S Timmerman 1 , avatar KK Brownlee 1 , avatar DA Rubin 1 , avatar AC Hackney 2

Endocrine Section, Applied Physiology Laboratory, Department of Exercise and Sport Science, and University of North Carolina, USA
Endocrine Section, Applied Physiology Laboratory, Department of Exercise and Sport Science, and Department of Nutrition, School of Public Health, University of North Carolina, *, USA
Warning: No corresponding author defined!
International Journal of Endocrinology and Metabolism: Vol.3, issue 1; 18-24
article type: Original Article
received: January 1, 2004
accepted: January 1, 2005

How To Cite Moore A, Timmerman S, Brownlee K, Rubin D, Hackney A. Strenuous, Fatiguing Exercise: Relationship of Cortisol to Circulating Thyroid Hormones. Int J Endocrinol Metab. 2005;3(1): 18-24. 

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<0.05). FG fT4 demonstrated a non significant increase from BO (FG fT4=1.84 ngldL)but by 24hR fT4 was significantly lower than FG (24hR fT4=1.67 ngldL, p (892.2 nmoljL) but returned to baseline by 24hR. Spearman correlation analysis yielded a significant negative correlation between FG cortisol and 24hR TSH (r= -0.65, p<0.05). A strong trend was also noted between FG cortisol and 24hR ft3 (r = -0.55, p<0.07).
Conclusion:? These findings suggest that exhaustive exercise decreases the level of selective thyroid hormones by 24 hours into recovery, and that cortisol levels after fatiguing exercise are negatively related to circulating TSH at this point into recovery.

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