Effect of long-term exercise-based interventions on thyroid function in hypothyroidism: A systematic review and meta-analysis of randomized controlled trials

Objective This study aimed to assess the effects of exercise interventions of more than 8 weeks on thyroid function in adults with hypothyroidism through a systematic review and meta-analysis of randomized controlled trials. Materials and methods The PEDro, WOS, PubMed, Cochrane Central Register of Controlled Trials, and Scopus databases were searched for relevant articles, which then underwent standardised screening, data extraction, and bias risk assessment. A total of seven randomised controlled trials (n = 7) were included, predominantly examining 12 weeks of exercise therapy. A meta-analysis was conducted using data extracted from the included studies. Standardised mean differences were calculated for thyroid-stimulating hormone levels, and heterogeneity was assessed using the I-2 statistic. The certainty of evidence was evaluated using the GRADE approach. Results Statistically significant reductions in thyroid stimulating hormone (TSH) levels (SMD: -3.254; 95 % CI: -3.937 to -2.572; p < 0.001) and increases in thyroxine (T4) level (SMD: 1.315; 95 % CI: 0.263-2.367; p = 0.015) were noted in exercise intervention groups as compared to control groups. Heterogeneity was moderate (I-2 = 65.93 %, p = 0.019) and no publication bias was detected. In addition, based on GRADE assessment, the certainty of evidence was rated as moderate for the TSH outcome and very low for the T4 outcome. Conclusion Findings from seven randomised controlled trials support the integration of long-term exercise as a non-pharmacological adjunct in the management of hypothyroidism. Exercise interventions, alongside conventional treatment, appear to improve thyroid function by reducing TSH and increasing T4 levels.