Abstract

Acute and prolonged exercises have controversial effect on the circulatory levels of thyroid hormones. The aim of the present study was to assess changes in thyroid hormones levels in elite top Jordanian athletes participating in both aerobic and anaerobic activities. Moreover, this work aims at comparing the level of thyroid hormones in both groups and to sedentary healthy subjects. Eighty Jordanian top level athletes with training experience of at least 5 years were included in this study. A group of healthy male and female adolescents (control group), matched for age and gender was also included (n = 50). Serum levels of free tri-iodothyronine (fT3), free thyroxin (fT4), thyroid-stimulating hormone (TSH) were examined. The results showed that although athletes showed normal levels of fT3, fT4 and TSH, the concentration of fT3 and TSH was significantly higher than control group. fT4 on the contrary, revealed significantly lower concentration compared to control. The levels of fT3, fT4 and TSH showed no significant differences between aerobic and anaerobic athletes. We concluded that long term exercise performed by athletes may have different impact on thyroid hormone levels in comparison with acute and intense exercise programs.

Key words: Athletes, thyroid hormones, free tri-iodothyronine (fT3), free thyroxin (fT4), thyroid-stimulating hormone (TSH).