All patient had blood thyroid stimulating hormone (TSH) levels measured before surgery and at 3, 6, 12, 18, and 24 months after bariatric surgery, and levothyroxine dose was changed as needed. At each visit, the levothyroxine dose was recorded as 1) total dose per day and 2) total dose/body weight (weight-based dose) per day.
At 24 months after bariatric surgery, the average total daily levothyroxine dose was significantly less in patients who had SG (133.7 mcg/day before surgery as compared to 104 mcg/day after surgery) while the average weight-based daily levothyroxine dose was unchanged (1.15 mcg/kg/ day before surgery and 1.11 mcg/kg/day after surgery). In contrast, the average total daily levothyroxine dose was unchanged in the RYGB group after surgery (129.5 mcg/ day before surgery and 125.2 mcg/day after surgery). While the dose of the group as a whole did not change, there was a marked variability in changes in total daily levothyroxine dose among the patients who underwent RYGB, with 41% requiring a decrease in dose, 41% no change, and 18% an increase in dose. However, the average weight-based daily levothyroxine dose increased in RYGB group (1.11 mcg/kg/day before surgery and 1.57 mcg/kg/day after surgery).
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that the levothyroxine requirements in patients with hypothyroidism change after bariatric surgery. Interestingly, while the total daily dose is more affected after SG than RYGB, the dose/body weight changed to a greater degree after RYGB than SG. Given the variability in changes in levothyroxine dose and potential need to decrease the levothyroxine dose after bariatric surgery, thyroid hormone levels should be closely monitored in patients with hypothyroidism for at least 24 months after bariatric surgery.
— Sun Lee, MD