This study aimed to systematically revise the available evidence on the effects of physical exercise training programmes on people with hypothyroidism. Comparative studies were searched in six electronic databases until April 2023. The Physiotherapy Evidence Database and the Methodological Index for Non-Randomized Studies were used to determine the methodological quality of the randomized controlled trials and comparative studies respectively. A total of 10 studies were found showing a low to moderate methodological quality. Most of them were performed in women with subclinical hypothyroidism. Exercise seemed to be safe, with aerobic and resistance training leading to improvements in outcomes related to physical and mental health. The performed meta-analysis with data from 120 participants indicated that exercise showed a non-significant trend towards reducing thyroid-stimulating hormone levels (Hedges'g -0.96; 95% CI -2.71; 0.79, p = 0.160; I2 = 92%). When the analysis was performed by comparing the experimental, and control groups with data from 180 participants the results remained non-significant (SMD -1.09; CI 95% -2.88; 0.70, p = 0.23; I2 = 95%). Similar findings were obtained when pooling data for FT3 and FT4 levels. Exercise does not have a significant impact on thyroid function, although its practice can lead to secondary outcomes related to physical and mental health.
Keywords: Thyroid hormones; exercise; hypothyroidism; systematic review; training.