An impact of bariatric surgery on thyroid function and medication use in patients with hypothyroidism.

Alex Zendel, MD¹, Yasmin Abu Ghanem, MD¹, Tal Yalon, MD¹, Yossi Dux, MD¹, Eyal Mor, MD¹, Galron Keren, MD², Dov Zippel¹, Moshe Rubin, MD¹, Aviram Nissan, MD¹, David Goitein, MD¹. ¹General Surgery C, Sheba Medical Center, Israel, ²Pediatric Emergency Department

Introduction: Bariatric surgery is effective in treating obesity associated co-morbidities. However, the effect of bariatric surgery on hypothyroid patients is less clear. On one hand, weight loss causes a change in thyroid hormone levels, particularly TSH reduction. On the other hand, bariatric surgery has an influence on drugs absorption, due to malabsorptive mechanism and by changing drug pharmacokinetics. The aim of our study is to assess the effect of bariatric surgery on thyroid function and on thyroid hormone therapy dosage in patients with hypothyroidism.

Methods: A retrospective analysis of all hypothyroid patients, who underwent bariatric surgery in our institution, between 2010-2014, was performed. The patients were evaluated for changes in thyroid hormone levels and in thyroid hormone replacement therapy dosage up to a year from surgery.

Results: Study included 86 patients; 79 female and 9 male at the average age of 47±12. The types of operations performed were laparoscopic sleeve gastrectomy in 71 (82.6%) and laparoscopic gastric bypass in 15 of patients. Patients BMI was significantly reduced from 43.9±6.5 before surgery to 34.6±5.7(P<0.001) and 29.8±5.7 (P<0.001), after 6 months and 1 year, respectively. TSH levels decreased significantly after 6 months from 4.1± 2.8 to 2.98±2.7 (P<0.05). TSH decrease after 1 year was not statistically significant. TSH decrease did not correlated with the degree of BMI reduction. At 1 year time point, patients required lower average dose of thyroid replacement therapy (P<0.02). Moreover, in 8 (9.3%) patients this therapy was completely stopped during 1 year of follow-up.    

Conclusion: Our study showed the favorable net effect of bariatric surgery on hypothyroid bariatric population, including improvement of thyroid function and reduction of thyroid medication dosages.  Further studies are required to evaluate an influence of thyroid replacement therapy absorption and to compare different types of bariatric operations.