Effect of Weight Loss after Bariatric Surgery on Thyroid-Stimulating Hormone Levels in Patients with Morbid Obesity and Normal Thyroid Function

Abstract

Background Several studies have reported that morbid obesity is associated with increased thyroid-stimulating hormone (TSH) levels. However, it is not clear what is the impact of bariatric surgery on postoperative thyroid function. The aim of this study was to evaluate the effect of weight loss after bariatric surgery on TSH levels in euthyroid patients with morbid obesity. TSH, free thyroxine (FT4), free triiodothyronine (FT3), type of surgery, and excessive body weight loss (EBWL) on TSH variation 12 months after surgery was evaluated. MethodsResults The high-normal TSH group (24.3% of patients) included more women, presented a higher BMI, higher systolic blood pressure, and higher FT3 levels. There was a significant decrease of TSH 12 months after surgery that was more marked in the high-normal TSH group (normal TSH group: 1.57 ± 0.49 to 1.53 ± 0.69 mIU/L, p = 0.063; high-normal TSH group: 3.23 ± 0.59 to 2.38 ± 0.86 mIU/L, p < 0.001). In a multivariate analysis, after adjusting for relevant covariates, EBWL, baseline BMI, and baseline FT3 were significantly associated with TSH decrease 12 months after bariatric surgery.Conclusion Bariatric surgery promotes a decrease of TSH that is significantly greater in patients with high-normal TSH and is independently associated with EBWL after surgery.

Central Resistance to Thyroid Hormones in Morbidly Obese Subjects Is Reversed after Bariatric Surgery-Induced Weight Loss

“…Increased FT4 in obesity has been found in some studies [14]. Several studies have reported different results regarding the variation of TSH after BS and the relation of TSH decrease with weight loss [15][16][17][18]. Most [15,17], but not all [18] studies have found a decrease in circulating TSH after the operation.…”

“…In agreement with our results, Guan et al [15] found that bariatric surgery was associated with a decrease in circulating TSH levels. Neves et al [17] found that BS promotes a significant decrease of circulating TSH. In obese children, weight loss was associated with a decrease in TSH, thyroid volume, and structure, while FT4 remained unchanged.…”

“…Several studies have reported different results regarding the variation of TSH after BS and the relation of TSH decrease with weight loss [15][16][17][18]. Most [15,17], but not all [18] studies have found a decrease in circulating TSH after the operation. In agreement with our results, Guan et al [15] found that bariatric surgery was associated with a decrease in circulating TSH levels.…”

“…The alteration of thyroid function and the effect of BS on thyroid function is not fully understood. There are previous studies showing different results regarding the variation of thyroid stimulating hormone (TSH) after weight loss surgery [15][16][17][18][19]. The free thyroxine (FT4) values in obesity and the variation after surgery are even more conflicting [15].…”

Improved Thyroid Hypoechogenicity Following Bariatric-Induced Weight Loss in Euthyroid Adults With Severe Obesity—a Pilot Study

“…In contrast, a retrospective cohort analysis of 55 euthyroid patients with severe obesity has previously reported that weight loss after RYGB significantly increases circulating fT4 levels, without affecting TSH (14). More recently, a large retrospective observational study in 949 euthyroid patients with severe obesity showed that bariatric surgery (laparoscopic adjustable gastric band, sleeve gastrectomy or RYGB) can result in a decrease in TSH levels, which is independently associated with the post-surgery excess body weight loss and is greater in patients with high-normal TSH (15). Overall, a recent meta-analysis on the impact of bariatric surgery on the thyroid function in patients with obesity has shown that decreased TSH, T3, and fT3 levels can be expected in these patients post-op, without significant changes in T4, fT4, and rT3 (12).…”