Hatice Gizem GUNHAN, Eren IMRE, Dilek GOGAS YAVUZ
Marmara Medical Journal - 2026;39(3):1-6
Objective: Obesity is associated with functional alterations in the hypothalamic-pituitary-thyroid (HPT) axis. Although bariatric surgery induces substantial weight loss and metabolic improvement, postoperative thyroid hormone changes and potential differences between surgical procedures remain unclear. Patients and Methods: This retrospective cohort study included 165 patients with obesity who underwent sleeve gastrectomy (SG, n=133) or Roux-en-Y gastric bypass (RYGB, n=32) between 2016 and 2020. Patients receiving thyroid-related treatment were excluded. Anthropometric, metabolic, and thyroid function parameters were assessed at baseline and 12 months postoperatively. Within-group and between-procedure changes were analyzed using nonparametric tests. Associations between hormonal and metabolic changes were evaluated using Spearman's rank analysis. Results: At baseline, 99.4% were euthyroid. At 12 months, significant reductions occurred in body weight, body mass index (BMI), fasting glucose, glycated hemoglobin (HbA1c), insulin, thyroid-stimulating hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3) (all p<0.001). SG and RYGB produced comparable reductions in weight and thyroid hormones, with no between-procedure differences. HbA1c reduction was greater after SG (p=0.021). Percentage TSH reduction was independently associated with percentage weight loss, while peripheral thyroid hormone changes showed weak correlations with glycemic parameters. Conclusion: Bariatric surgery leads to modest thyroid hormone reductions in untreated euthyroid patients, independent of surgical technique and likely reflecting physiological metabolic adaptation rather than thyroid dysfunction.
