Preoperative Thyroid Autoimmune Status and Changes in Thyroid Function and Body Weight After Bariatric Surgery

Bariatric surgery has emerged as the most effective therapy for morbid obesity. There is increasing evidence that bariatric surgery could alleviate systemic inflammation and influence thyroid function. The current study aimed to investigate the associations of preoperative thyroid autoimmune status with the changes in body weight and thyroid function after bariatric surgery.

We recruited 101 patients with morbid obesity (44 men and 57 women) who received bariatric surgery at Zhongshan Hospital, Fudan University. Those who had used thyroid hormone replacement or antithyroid drugs were excluded. General linear models were used to compare the changes in body weight and thyroid function in participants with different thyroid autoimmune statuses.

After bariatric surgery, serum-free triiodothyronine (FT3) (4.94 ± 0.73 vs 4.33 ± 0.59 pmol/L, P < 0.001) and thyroid-stimulating hormone (TSH) (3.13 ± 1.59 vs 2.26 ± 1.26 μIU/mL, P < 0.001) were significantly reduced, accompanied by reductions in BMI (42.1 ± 7.6 vs 31.4 ± 6.5 kg/m², P < 0.001), and estimated basal metabolic rate (2002 ± 398 vs 1700 ± 336 kcal/day, P = 0.001) and an improvement in lipid profiles. Serum thyroperoxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) levels also decreased significantly from 79.3 and 177.1 IU/mL to 57.8 and 66.0 IU/mL in participants with positive thyroid antibodies (P < 0.05). Further analysis showed that the positive preoperative thyroid autoimmune status was associated with less reduction in serum TSH (0.05 ± 1.59 vs - 1.00 ± 1.43 μIU/mL, P = 0.021) and BMI (- 8.3 ± 3.6 vs - 11.0 ± 4.5 kg, P = 0.049) after bariatric surgery.

Our study highlights a group of patients with morbid obesity, who have positive preoperative thyroid autoimmunity and less reduction in serum TSH levels and body weight after bariatric surgery.