Effect of bariatric surgery on TSH levels and levothyroxine dosage in patients with thyroid disease

Abstract

Objectives Bariatric surgery might impact on the thyroid function test and, in hypothyroid patients, the dose of levothyroxine (LT4), but data are not univocal. We examined the change of thyroid function in the first year after bariatric surgery in euthyroid patients and in patients with thyroid disease on LT4 comparing the effects of Roux-en-Y gastric bypass (RYGB) vs sleeve gastrectomy (SG). Methods The data was collected from medical records of hospitalization of 235 patients (104 SG and 131 RYGB) who underwent pre-surgical work-up and from outpatient medical records of the same patients at 45 days, 3–6 months and 1-year visits after surgery. In the final analysis we included 69 patients on LT4 therapy (43 Tr-RYGB and 26 Tr-SG) and 85 patients without thyroid diseases with normal thyroid function (48 Ct-RYGB and 37 Ct-SG), who served as matched controls. Results The mean body weight reduction for al cohort was in 31.4 ± 0.7% after 1 year from the surgery. In the two Nt groups, TSH levels remained stable throughout the observation period, without differences for type of surgery and without relationship with body weight. After bariatric surgery, the patients treated with LT4, belonging to both Tr-RYGB and Tr-SG, needed to increase the dosage per body weight to achieve stable TSH. At 1 year, the increase of LT4/kg/die was higher in the Tr-RYGB group than Tr-SG group (0.44 vs 0.30 mcg/kg/die, p = 0.032). Conclusions In patients with severe obesity and normal thyroid function, TSH levels are not related to body weight change. Patients treated with LT4, after bariatric surgery need to increase the dosage pro kg of body weight of the LT4 and the increase is higher after surgery with malabsorptive component (RYGB) compared to restrictive surgery (SG).