Time Trends in Thyroid Hormone Changes Following Bariatric Surgery: A Systematic Review and Meta-Analysis

Previouarch indicates varyings rese effects of bariatric surgery on thyroid function. This meta-analysis aims to evaluate time-dependent changes in thyroid hormone levels following bariatric surgery in patients with obesity.

PubMed, Embase, and Scopus databases were systematically searched until July 2025 for observational studies including patients with obesity (body mass index ≥ 30 kg/m²) undergoing bariatric surgery, reporting changes in thyroid-stimulating hormone (TSH), free thyroxine (T4), or free triiodothyronine (T3) following surgery. A random-effects model was used for the meta-analysis, with meta-regression and subgroup analyses to evaluate the impact of age, sex, region, preoperative thyroid function, and surgery type on outcomes.

A total of 57 studies with 8,030 participants were included. Significant reductions in TSH and FT3 levels were observed at 6-month (TSH: SMD: -1.43, 95% CI: -2.22 to -0.63; FT3: SMD: -1.89, 95% CI: -3.14 to -0.65) and 1-year (TSH: SMD: -1.38, 95% CI: -2.44 to -0.31; FT3: SMD: -2.14, 95% CI: -3.52 to -0.75). However, these reductions became non-significant at > 1-year follow-ups. No significant changes were observed in FT4 levels across all follow-up periods. Subgroup analyses indicated significant reductions in TSH and FT3 following sleeve gastrectomy, Roux-en-Y gastric bypass, and gastric banding, while bilio-pancreatic diversion did not result in significant hormone changes.

Bariatric surgery leads to significant reductions in TSH and FT3 levels at 6-month and 1-year follow-ups, with no significant change in FT4 level. Further studies are needed to explore the mechanisms of thyroid changes after bariatric surgery and develop strategies to optimize thyroid health in these patients.