Total weight loss induces the alteration in thyroid function after bariatric surgery.

Background: Bariatric surgery is an effective approach to weight loss, which may also affect thyroid function. However, alteration in thyroid-stimulating hormone (ΔTSH) and thyroid hormones after bariatric surgery and the relationship between thyroid function and postoperative weight loss still remains controversial. Methods: Data were collected from euthyroid patients with obesity who underwent sleeve gastrectomy and Roux-en-Y gastric bypass from 2017 to 2022. The alterations of free thyroxine (FT4), free triiodothyronine (FT3), total thyroxine (TT4), total triiodothyronine (TT3), and TSH were calculated 1 year after surgery. Pearson correlation analysis was used to assess the correlation between the percentage of total weight loss (%TWL) and ΔTSH. Multivariable linear regression was utilized to determine the association between %TWL and ΔTSH. Results: A total of 256 patients were included in our study. The mean %TWL was 28.29% after 1 year. TSH decreased from 2.33 (1.67, 3.04) uIU/mL to 1.82 (1.21, 2.50) uIU/mL (P < 0.001), FT3 decreased from 3.23 ± 0.42 pg/mL to 2.89 ± 0.41 pg/mL (P < 0.001), FT4 decreased from 1.11 ± 0.25 ng/dL to 1.02 ± 0.25 ng/dL (P < 0.001), TT3 decreased from 1.13 (1.00, 1.25) ng/mL to 0.89 (0.78, 1.00) ng/mL (P < 0.001), and TT4 decreased from 8.28 ± 1.69 ug/mL to 7.82 ± 1.68 ug/mL 1 year postoperatively (P < 0.001). %TWL was found to be significantly correlated to ΔTSH by Pearson correlation analysis (Pearson correlation coefficient = 0.184, P = 0.003), indicating that the more weight loss, the more TSH declined. After adjusting for covariates in multivariable linear regression, %TWL was found to be independently associated with ΔTSH (ß = 0.180 [95% confidence interval (CI), 0.048 - 0.312], P = 0.008). Moreover, %TWL was divided into 3 categorical groups (%TWL ≤ 25%, 25% < %TWL ≤ 35%, and %TWL > 35%) for further exploration, and was also found to be an independent predictor for ΔTSH after adjusting for covariates in multivariable linear regression (ß = 0.153 [95% CI, 0.019 - 0.287], P = 0.025). Conclusion: TSH, FT4, FT3, TT4, and TT3 decrease significantly 1 year after bariatric surgery. The decline in TSH is independently mediated by postoperative weight loss; the more the weight loss, the more the TSH decrease.

Prevalence of anemia and related nutrient deficiencies after sleeve gastrectomy: A systematic review and meta-analysis.

This study aimed to investigate the prevalence of anemia and related nutrient deficiencies after sleeve gastrectomy (SG). Four online databases were searched for relevant articles. Thirty-one studies with 7639 patients were included in the meta-analysis. The pooled anemia prevalence was 7%, 6%, 9%, 10%, 12%, 25%, 20%, and 18% at baseline, 3 months, 6 months, 12 months, 24 months, 36 months, 48 months, and 60 months, respectively. Although the prevalence of vitamin B12 and folate deficiencies remained low postoperatively, the prevalence of ferritin deficiency steadily increased from 6% at baseline to 27% at 60 months. The prevalence of serum iron deficiency decreased from 13% at baseline to 6% at 24 months and increased to 20% at 60 months. Anemia and ferritin deficiency were strongly correlated (Pearson correlation coefficient = 0.774, p = 0.041). Subgroup analysis suggested that age ≤40 years, preoperative anemia, and insufficient iron supplementations were high-risk factors for postoperative anemia. SG is associated with an increased risk of anemia and decreased iron storage over long-term observation. Routine iron supplementations may reduce anemia after SG; however, the dosages recommended by current guidelines may be insufficient. More strict monitoring schedules and supplementation strategies should be established for the timely detection and management of postoperative anemia.