The effects of levothyroxine substitution on body composition and body mass after total thyroidectomy for benign nodular goiter

Many patients who have undergone total thyroidectomy complain about weight gain and changes in body composition. This prospective study was designed to evaluate the effect of thyroxine replacement on body mass index (BMI) and body composition following total thyroidectomy for benign multinodular goiter. Thirty-three consecutive patients were enrolled. The patients of those histopathological examination revealed carcinoma (n=5) and who did not present for the 6th month follow-up visit (n=6) were excluded. Thyroxine (T4, 100 μg, dose range 50-200 μg) was started in all patients immediately after the surgery and adjusted according to plasma TSH and FT4-FT3 levels in the postoperative 3rd week and postoperative 3rd and 6th months respectively to achieve optimal TSH within normal reference range (0.5- 4.2 mU/L). Changes in weight, BMI and anthropometric measurements were performed preoperatively and in the postoperative 3rd and 6th months. The study completed with 22 patients (17 female and 5 male, mean: 45.8 years; range: 26-64 years). Fourteen patients maintained euthyroid status and eight had subclinical hypothyroidism. There were no significant differences between the subclinical hypothyroid and euthyroid patients in BMI and the other anthropometric values (p>0.05). In the comparisons for age, there were significant changes with regarding weight and BMI. Increases in weight were noted as 2.2±2.7 kg in age over 45 (n= 14, mean: 52.7 years, range: 46-64 years), while 0.1±1.3 kg in age under 45 years (mean; 33.8, range: 26-43 years) and BMI as 0.8±1.0 in age over 45 years compared to 0.04±0.5 in age under 45 years, respectively (p=0.025 and p=0.029, respectively). No significant differences were noted in other anthropometric parameters at the end of 6th month compared to the baseline value except the triceps skin fold (p=0.027). Levothyroxine replacement had no effect on their body composition; however, age was found to be an important factor for weight gain and change in BMI during the midterm follow-up period.