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TOPLINE:

A year after bariatric surgery, greater weight loss is linked to measures of improved thyroid function in euthyroid patients with obesity.

METHODOLOGY:

• Obesity is associated with higher levels of thyroid-stimulating hormone (TSH) than normal weight, but changes in TSH and thyroid hormones after bariatric surgery in euthyroid individuals are still debatable.
• This study evaluated changes in TSH and thyroid hormones 1 year after bariatric surgery in 256 Chinese patients with obesity (body mass index [BMI] ≥ 27.5; 64.8% women) who underwent sleeve gastrectomy and Roux-en-Y gastric bypass at China-Japan Friendship Hospital between September 2017 and May 2022.
• The patients (median age, 35 years; baseline average BMI, 38.37 ± 7.24; 57.8% diagnosed with type 2 diabetes) had normal preoperative TSH and free thyroxine levels.
• The changes in serum TSH, free thyroxine, free triiodothyronine, total thyroxine, and total triiodothyronine levels were measured 1 year after surgery.
• The association between the percentage of total weight loss (TWL) and changes in TSH levels was assessed as continuous and categorical (%TSL ≤ 25%, 25% to ≤ 35%, and > 35%) variables using Pearson correlation analysis.

TAKEAWAY:

• The mean percentage of TWL was 28.62% at 1 year after bariatric surgery.
• Overall, serum levels of TSH, free thyroxine, free triiodothyronine, total thyroxine, and total triiodothyronine reduced significantly 1 year after bariatric surgery (all P < .001).
• After adjusting for several covariates, the percentage change in TWL individually and by groups independently predicted lower TSH levels (β, 0.180; P = .008) and (β, 0.153; P = .025), respectively.

IN PRACTICE:

The findings provide "physiological encouragement for the clinical therapeutic strategy of surgical treatment for obesity-related thyroid dysfunction," wrote the authors. "TSH will decrease following weight loss after bariatric surgery in patients with TSH levels approaching the upper normal limit, without the need for additional thyroid hormone-lowering medication," they further added.

SOURCE:

The study was conducted by first author Ziru Tian, Department of General Surgery & Obesity and Metabolic Disease Center, China-Japan Friendship Hospital, Beijing, China. It was published online in Frontiers in Endocrinology.

LIMITATIONS:

There was selection bias because of the retrospective, single-center nature of the study. The study findings may not be applicable to Western populations because this study included only Chinese patients with obesity. Moreover, changes in thyroid function after 1 year and the effect of weight regain on thyroid function could not be investigated.

DISCLOSURES:

This study was supported by the China-Japan Friendship Hospital National High Level Hospital Clinical Research Funding, the National High Level Hospital Clinical Research Funding, and the Elite Medical Professionals Project of China-Japan Friendship Hospital. The authors declared no potential conflicts of interest.