Preoperative vitamin D and vitamin B12 as predictors of TSH remission after sleeve gastrectomy.

BACKGROUND

Thyroid function may improve after bariatric surgery; however, predictors of postoperative TSH remission are not well defined. We investigated whether preoperative vitamin D and B12 levels could predict TSH remission after sleeve gastrectomy in patients with hypothyroidism.

METHODS

This single-center retrospective cohort study included adults with preoperative hypothyroidism who underwent laparoscopic sleeve gastrectomy between February 2021 and December 2024 at our institution. The primary outcome was 6-month TSH remission, defined as a TSH level of 0.5-4.0 mIU/L without levothyroxine (LT4) dose increase. The secondary outcomes included 12-month remission and changes in the LT4 dose. Multivariate logistic regression was adjusted for age, sex, BMI, vitamin D, and vitamin B12; penalized (Firth) regression was applied to address separation. The predictive performance was evaluated using ROC analysis.

RESULTS

Of 289 patients, 40 (13.9%) met the inclusion criteria (mean age 46.3 ± 7.4 years; 75% female). TSH remission occurred in 67.5% and 77.5% of patients at 6 and 12 months, respectively. Patients who achieved remission had significantly higher preoperative vitamin B12 and vitamin D levels at both time points (all p ≤ 0.007). No patient required LT4 dose escalation; dose reduction or withdrawal occurred in 70.0% of patients by 12 months. ROC analysis demonstrated strong discrimination at 6 months (vitamin B12 AUC 0.858; vitamin D AUC 0.826) and excellent discrimination at 12 months (vitamin B12 AUC 0.841; vitamin D AUC 0.898). Vitamin D showed a near-significant association with 12-month remission (OR 1.30 per 1 ng/mL; p = 0.051).

CONCLUSIONS

Higher preoperative vitamin D and vitamin B12 levels strongly predicted TSH remission after sleeve gastrectomy, supporting routine micronutrient assessment and prospective validation of these findings.