Changes in Thyroid Replacement Therapy after Bariatric Surgery: Differences between Laparoscopic Roux-en-Y Gastric Bypass and Laparoscopic Sleeve Gastrectomy.

INTRODUCTION: Levothyroxine (LT4) requirements can presumably be modified differently after laparoscopic Roux-en-Y gastric bypass (LRYGB) and laparoscopic sleeve gastrectomy (LSG). The present study compared changes in LT4 dose in hypothyroid subjects undergoing LRYGB or LSG 2 years after the procedure. MATERIAL AND METHODS: A 2-year follow-up observational study was conducted in a prospective cohort of obese patients who had undergone bariatric surgery and were receiving LT4. Indication for the type of surgical procedure was based on clinical criteria. Repeated measures ANOVA models were used to examine differences within and between groups. RESULTS: Thirty-five consecutive patients were included for analysis: 22 LRYGB and 13 LSG. Total daily LT4 dosage decreased in the LSG group (133.7 ± 50.3 mcg/day at baseline to 104.3 ± 43.3 mcg/day at 2 years; p = 0.047) whereas it remained stable in the LRYGB group (129.5 ± 46.1 mcg/day at baseline to 125.2 ± 55.7 mcg/day at 2 years; p = 1.000). Differences between groups became significant at 24 months. Daily weight-based LT4 dose increased in the LRYGB group (1.11 ± 0.38 mcg/kg day at baseline to 1.57 ± 0.74 mcg/kg day at 2 years; p = 0.005) with no significant changes in the LSG group (1.15 ± 0.35 mcg/kg day at baseline vs 1.11 ± 0.49 mcg/kg day at 2 years; p = 1.000). CONCLUSION: LRYGB and LSG showed different changes in LT4 requirements 2 years after surgery. There was an early decrease in daily total LT4 dose requirements after LSG, which suggests an early preventive reduction to be validated in future studies.