Thyroid Function and Anthropometric Measures: A Systematic Review and Meta-Analysis.

OBJECTIVE

Although often enquired about by patients, the association of thyroid function with anthropometric measures in the general population is unclear. We summarized population-based studies and randomized controlled trials (RCTs) on the association between thyroid function and anthropometric measures.

METHODS

We systematically searched Embase, Medline (Ovid), and Cochrane Central Register of Controlled Trials from inception until June 28, 2023. We included studies in adults examining thyroid function or thyroid disease as exposure and anthropometric measures as outcome (eg, body mass index [BMI], weight). We used random effect meta-analyses to pool the results.

RESULTS

We included 64 studies in the qualitative synthesis, and 21 in the quantitative synthesis (total participants n = 107 734 for cross-sectional studies, n = 22 010 for longitudinal studies, n = 80 for RCTs). The evidence was limited and heterogeneous, particularly for longitudinal studies. Cross-sectionally, we described an association for thyroid-stimulating hormone (TSH) concentrations and BMI (B per 1 mIU/L increase of TSH = 0.21; 95% confidence interval [CI], 0.09-0.32) and for free thyroxine (FT4) and BMI (B = -0.14; 95% CI, -0.23 to -0.05). Longitudinally, increasing TSH concentrations were related to weight gain and increasing FT4 concentrations to weight loss.

CONCLUSION

We showed a relation between higher TSH concentrations and higher BMI or weight, and between higher FT4 concentrations and lower BMI or weight, although effect sizes were modest. We highlight the need of more high-quality longitudinal studies. Despite the relevance of the association between thyroid (dys-)function and anthropometric measures, evidence is scarce.