[The analysis of exercise efficiency and autonomic function in children with nontoxic nodular goiter during...

The aim of the study was the analysis of exercise efficiency and the function of the autonomic system in children with a nontoxic nodular goiter (NNG) subjected to TSH suppression. The study comprised 17 children, aged 11-18 years, with NNG treated with suppressive L-thyroxine doses for 6-36 months (mean 24 months). Exercise efficiency was examined on a moving track according to the protocol of Bruce. Analysis of the autonomic function was based on functional tests of the circulatory system and monitoring of the QTc interval. A group of healthy children with a negative heart and thyroid history served as control. Statistically significant acceleration of the heart rate (p<0.01) was found in NNG patients subjected to TSH suppression, compared with controls. The remaining results included a fall in exercise efficiency parameters:work load (p<0.001) and duration (p<0.003), metabolic equivalent (p<0.005), and the maximal oxygen consumption index Vo2 (p<0.005) at normal values of double product. A significant decrease was revealed in the ejection fraction during exercise (61+/-1.9 vs 67+/-5.9 p<0.001) in the group of children with nontoxic nodular goiter.

1. In the subclinical state of hyperthyroidism no functional disorders were observed in the autonomic system, which controls the circulatory system. 2. Exercise tolerance was reduced in patients with nontoxic nodular goiter subjected to TSH suppression. 3. A relationship was found between the level of thyroid hormones (TSH, FT4) indicating the subclinical state of hyperthyroidism and the acceleration of heart rate, reduction in the ejection fraction of the left ventricle of the heart after exercise and shortening of load test duration. 4. Higher rest values of heart rate were observed in children treated with suppressive doses of L-thyroxine, compared with controls.