Levothyroxine dose adjustment in hypothyroid patients following gastric sleeve surgery.

Abstract Introduction: Euthyroid patients show decreased TSH level following sleeve gastrectomy. However, studies of levothyroxine absorption after bariatric surgery reported contradictory results and data on levothyroxine dose adjustment according to weight are sparse. The aim of this study was to evaluate levothyroxine dose adjustment during weight loss following sleeve surgery. Method: This retrospective study assessed change in levothyroxine dose in patients undergoing sleeve gastrectomy at the university hospital center of Nimes (France) between January 2010 and March 2016. Patients were receiving standard bariatric surgery follow-up with levothyroxine therapy for hypothyroidism. Results: Fifty-two of the 271 patients who underwent sleeve gastrectomy (19.2%) were being treated with levothyroxine. Twenty-one were excluded; 31 were followed up for 12 months, including 12 who were followed up for 24 months. Mean weight loss was 35±11 kg at 12 months and 41.8±10.2 kg at 24 months. Daily levothyroxine dose decreased from 108 [88-144] µg/day to 94 [63-125] µg/day at 12 months and 69 [44-134] µg/day at 24 months, with positive correlation between dose and weight loss at 12 months (P=0.03). Weight-adjusted dose was 1.04 [0.81-1.24] µg/kg/day at baseline, 1.14 [0.85-1.66] µg/kg/day at 12 months, and 0.85 [0.53-2.10] µg/kg/day at 24 months, showing no correlation with weight loss. Median TSH level dropped to 1.30 [0.63-2.27] mIU/l at 12 months and 1.48 [1.08-2.42] mIU/l at 24 months. Conclusion: Despite a decrease in daily levothyroxine dose correlating with weight loss at 12 months, the absence of correlation with weight-adjusted dose suggests the involvement of confounding factors such as poor drug absorption or altered thyroid function. Further studies are required to elucidate the absorption of levothyroxine.