Recent studies have shown that obesity is associated with increased thyroid-stimulating hormone (TSH) and thyroid hormones. Thyroid hormones regulate basal metabolism, and thermogenesis, and play an important role in lipid and glucose metabolism, food intake, and fat oxidation. However, the influence of body fat distribution on this relationship remains unclear. The findings of a recent retrospective observational study reported that metabolic surgery significantly alters thyroid function and hormone resistance in obese patients, with changes closely tied to reductions in fat mass and increases in muscle mass. These findings suggest that bariatric surgery not only aids weight loss but also has profound effects on thyroid health, potentially improving thyroid hormone resistance in obesity. The study, led by Dr. Yu Yan and his team, was published in the Journal of Clinical Endocrinology & Metabolism.
Yan et al. analyzed data from 470 obese patients (mean age 33.4 years; mean BMI 37.9; 63.2% women) and 118 non-obese controls (mean BMI 21.8), all with normal TSH, free triiodothyronine (fT3), and free thyroxine levels. Among the obese patients, 125 underwent metabolic/bariatric surgery and had thyroid tests before and at least three months after surgery. The results showed that obese individuals had significantly higher baseline TSH and fT3 levels (P <0.001) and thyroid feedback quantile-based index (TFQI; P = .047) compared to controls, with all values decreasing post-metabolic surgery (P <0.001). Preoperative TSH positively correlated with visceral fat area (VFA; P = 0.019) and body fat percentage (P =0.013), and negatively with skeletal muscle mass percentage (P = 0.024). Metabolic surgery significantly impacts thyroid function and thyroid hormone resistance, with notable correlations to changes in body composition. The reduction in TSH after metabolic surgery was significantly associated with decrease in VFA (P = .021) and body fat percentage (P = .031). Improved central thyroid hormone resistance, as indicated by reduced TFQI, was linked to reductions in both VFA and body fat percentage after metabolic surgery
The bidirectional relationship between obesity and thyroid hormones suggests that addressing thyroid disturbances may aid weight loss and improve metabolic health. In a retrospective observational study conducted at two centers in Taif, Saudi Arabia, Alfaifi et al. concluded that bariatric surgery leads to improved thyroid profiles and lower levothyroxine dosage, indicating an improvement in hypothyroidism.
The study indicates that metabolic surgery not only facilitates weight loss but also improves thyroid function and reduces thyroid hormone resistance, especially through changes in body composition. These findings support the integrated management of thyroid and metabolic health in obese patients undergoing bariatric surgery, making it critical for clinicians to monitor and address thyroid function as part of the post-surgical care plan.
References
- Yan Y, Chu X, Wang J, Kang X, Shan X, Yu H, et al. Alterations in Thyroid Hormones in Obese Patients are Associated with Body Composition Changes after Bariatric Surgery. The Journal of Clinical Endocrinology & Metabolism. 2024 Sep 2;dgae605.
- Alfaifi HH, Altowairgi MA, Algethami RG, Altowairqi AH, Althomali HD, Almalki OM. Effectiveness of Bariatric Surgery for Improving Thyroid Function and Reducing Levothyroxine Dose in Patients With Obesity and Overt Hypothyroidism. Cureus. 15(5):e38780.
- Sanyal D, Raychaudhuri M. Hypothyroidism and obesity: An intriguing link. Indian Journal of Endocrinology and Metabolism. 2016 Aug;20(4):554.