Changes in levothyroxine pharmacokinetics following bariatric surgery in obese hypothyroid patients

Aim: Levothyroxine (L-T4) requirements in obese hypothyroid patients receiving L-T4 therapy decrease following bariatric surgery. L-T4 absorption is also thought to decrease after surgery. The purpose of this study was to evaluate L-T4 requirements in hypothyroidism cases before and after weight loss through bariatric surgery. Methods: Seventy-six cases of hypothyroidism receiving L-T4 replacement therapy and with a body mass index over 40 kg/m2 were included in the study. Patients losing at least 10% of basal body weight following bariatric surgery were assessed in terms of thyroid hormone levels and L-T4 requirements over follow-up of at least one year. The L-T4 requirements of patients in whom euthyroidism was achieved were compared in terms of bariatric surgery procedures and hypothyroidism etiology. Results: Seventy-six patients (56 women, 20 men) with a mean age of 38 years (18-51) were included in the study. Mean weight before bariatric surgery was 121.6 ± 6.8 kg, and mean body mass index was 49.5 ± 1.6 kg/m2. Euthyroidism was confirmed at pre- and post-bariatric surgery evaluation. No statistically significant postoperative changes were determined in thyroid-stimulating hormone or free thyroxine-3 and -4 (p > 0.05). A statistically insignificant decrease was observed in L-T4 dosages after surgery in cases of Hashimoto’s thyroiditis (p = 0.064). A statistically significant decrease was determined in L-T4 dosages in cases of non-Hashimoto hypothyroidism (p = 0.001). L-T4 requirements decreased in both surgical procedures (p = 0.001) Conclusion: Postoperative L-T4 requirements decrease with weight loss. In addition, no decrease appeared to occur in L-T4 absorption following the surgical procedures in this study.


[1] Bernadette B. Thyroid and Obesity: An Intriguing Relationship. J Clin Endoc Metabol. 2010;8(1):3614–17.

[2] Sanyal D, Raychaudhuri M. Hypothyroidism and obesity: An intriguing link. Indian J Endocrinol Metab. 2016;20(4):554–57.

[3] Gadiraju S, Lee CJ, Cooper DS. L-T4 Dosing Following Bariatric Surgery. Obes Surg. 2016;26(10):2538–42.

[4] Longhi S, Radetti G. Thyroid function and obesity. J Clin Res Pediatr Endocrinol. 2013;5(1):40–44.

[5] Zendel A, Abu-Ghanem Y, Dux J, et al. The Impact of Bariatric Surgery on Thyroid Function and Medication Use in Patients with Hypothyroidism. Obes Surg. 2017;27(8):2000–4.

[6] Gokosmanoglu F, Aksoy E, Onmez A, et al. Thyroid Homeostasis After Bariatric Surgery in Obese Cases. Obes Surg. 2020;30(1):274–78.

[7] Juiz-Valiña P, Cordido M, Outeiriño-Blanco E, et al. Central resistance to thyroid hormones in morbidly obese subjects is reversed after bariatric surgery-induced weight loss. J Clin Med. 2020;9(2):359.

[8] Guan B, Chen Y, Yang J, et al. Effect of bariatric surgery on thyroid function in obese patients: a systematic review and meta-analysis. Obes Surg. 2017; 27(12):3292–305.

[9] Yang J, Gao Z, Yang W, et al. Effect of sleeve gastrectomy on thyroid function in chinese euthyroid obese patients. Surg Laparosc Endosc Percutan Tech. 2017;27(4):66–68.

[10] Michalaki MA, Gkotsina MI, Mamali I, et al. Impaired pharmacokinetics of L-T4 in severely obese volunteers. Thyroid. 2011;21(5):477–81.

[11] Nannipieri M, Cecchetti F, Anselmino M, et al. Expression of thyrotropin and thyroid hormone receptors in adipose tissue of patients with morbid obesity and/or type 2 diabetes: effects of weight loss. Int J Obesity. 2009;33(9):1001–6.

[12] Fallahi P, Ferrari SM, Camastra S, et al. TSH normalization in bariatric surgery patients after the switch from L-T4 in tablet to an oral liquid formulation. Obes Surg. 2017;27(1):78–82.

[13] Santini F, Pinchera A, Marsili A, et al. Lean body mass is a major determinant of L-T4 dosage in the treatment of thyroid diseases. J Clin Endocrinol Metab. 2005; 90(1):124-27.

[14] Rubio IG, Galrão AL, Santo MA, et al. L-T4 absorption in morbidly obese patients before and after Roux-En-Y gastric bypass (RYGB) surgery. Obes Surg. 2012; 22(2):253–58.

[15] Gkotsina M, Michalaki M, Mamali I, et al. Improved L-T4 pharmacokinetics after bariatric surgery. Thyroid. 2013;23(4):414–19.

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