Comparison between different methods of adjustment of thyroxin replacement dose after total thyroidectomy for bengin thyroid disease

Introduction: Levothyroxin (T4) is commonly employed to correct thyroid hormone deficiency from various causes, and as total thyroidectomy is increasingly used to treat benign thyroid conditions, lifelong treatment with optimal dose of thyroxin (T4) is required which is difficult to predict. This study investigated factors that might predict the ideal T4 dose, and testing the body mass index as predictive factor with the aim of reducing delays in achieving normal thyroid function after surgery.
Methods: This study was conducted on 52 patients presented with benign thyroid disease and operated upon with total thyroidectomy. The patients were prospectively randomized into two comparable groups of patients. One group of patients was given the routinely used titration method of thyroid replacement therapy, while the other used an algorithm for T4 dosage based on patient weight (postoperative weight) which was subsequently applied in previous published literatures. Patient and operative variables that might predict time to achieve normal thyroid function and optimal T4 replacement dose were examined.
Results: The median time to achieve normal thyroid function was 16 (range 8–33) weeks in the first group in which the traditional titration method was used and large changes in T4 dose needed. But it was only 8 (range 4-17) weeks in the second group in which the weight algorithm was used. In multivariate analysis, the best predictor of optimal T4 dose was body weight. The use of a weight-related algorithm improved time to achieve normal thyroid function. There was a much stronger association between the L-T4 dosage and body mass.
Conclusion: The T4 replacement dosage after total thyroidectomy is largely influenced by body weight particularly in subjects with high BMI values. Use of a weight-related algorithm shortens the time required to attain a stable dose of L-T4 compared with use of standard T4 dose-titration methods