Endocrine Abstracts

Objectives: Bariatric surgery significantly impacts various aspects of health, including thyroid function. Despite this, there is a lack of clear data on whether patients taking levothyroxine should adjust their dosing regimen following weight loss post-bariatric surgery. Bariatric surgery alters the anatomy of the gastrointestinal tract, potentially affecting medication absorption, including levothyroxine. Procedures such as gastric bypass and sleeve gastrectomy can lead to changes in gastric pH, reduced stomach volume, and modified intestinal transit time, all of which may affect drug absorption. Therefore, immediate postoperative levothyroxine dosages may require adjustment to ensure adequate thyroid hormone replacement therapy. Understanding these changes is crucial for managing thyroid health in individuals undergoing bariatric surgery.

Methods: We investigated 30 patients (n = 30) with 3rd-degree obesity (BMI > 40 kg/m²) and hypothyroidism who underwent bariatric procedures. The study population comprised mostly women; 8 out of 30 (26.7%) underwent Roux-en-Y gastric bypass, and the remaining 22 (73.3%) underwent sleeve gastrectomy. The patients were assessed for levothyroxine dosing up to 12 months after surgery. The weight reduction was up to 40% from additional weight with different variations compared to baseline.

Results: The study showed that patients who underwent gastric bypass often require higher doses of levothyroxine to maintain euthyroidism post-surgery. Compared with baseline, the absolute LT4 dose and LT4 dose/kg of ideal body weight were, on average, 20% higher 12 months after surgery. In contrast, data from patients who underwent sleeve gastrectomy indicated a decrease in absolute LT4 dose and LT4 dose/kg by up to 10-15% compared to pre-surgery levels. Factors such as rapid weight loss, altered gastrointestinal physiology, and changes in drug absorption contribute to the increased dosage requirements, which are more prevalent in the case of gastric bypass. In the case of sleeve gastrectomy, LT4 dosage is adjusted more based on weight loss, and changes in drug absorption are less evident compared with gastric bypass. Clinical guidelines for dosage adjustments take into account the type of surgery performed, the extent of weight loss, thyroid function tests, and individual patient characteristics. Close monitoring of thyroid hormone levels, along with clinical symptoms, helps determine appropriate dosage adjustments to optimize thyroid function and overall health outcomes.

Conclusion: Bariatric surgery can influence thyroid hormone metabolism and necessitate adjustments in levothyroxine dosage to maintain optimal thyroid function. Further investigations are needed to confirm thyroid hormone dose adjustments after bariatric procedures, taking into account the type of surgery performed.