Body Weight Changes in Hypothyroid Patients after Treatment with Levothyroxine

Introduction: Body weight changes after initiation of levothyroxine in newly diagnosed hypothyroid patients is induced by some mechanisms but some studies report weight gain after treatment. The aim of our study is to investigate the weight changes and related factors after initiation of levothyroxine therapy.Materials and Methods: This is a retrospective study on medical records of 120 newly diagnosed primary hypothyroidism. The patient’s age was 18-60 years old of both sexes. Patients with post-surgical hypothyroidism, thyroid cancer, history of head and neck radiation, pregnancy, anorexia nervosa and end stage diseases were excluded. TSH, weight and body mass index (BMI) were recorded at the time of diagnosis, three months after initiation of levothyroxine and a median follow up of 45 months.Results: A total of 120 patients (mean age 40 ± 13 years, 86.7% women) were included. Out of 120 subjects, 66.7% had clinical and overt hypothyroidism and 33.3% subclinical hypothyroidism. Initial median TSH was 23.3 mIU/L (4.7-100) and weight was 73.2kg (40-105). Post treatment median TSH was 3.5 mIU/L (0.03-26)) and weight change after 3 month was -1.3±3.4 kg (-13 - 6). Mean BMI at base was 28.6 kg/m2 (18.8 - 42.2) and the mean change of BMI was1.26 ± 0.42 kg/m2 (-4.8 – 2.1). Only 41.7% of patients lost weight. 50% of patients had weight gain and 8.8 % of patients had no weight changes. The basal BMI, weight and TSH had negative correlation with weight change (p<0.05).Sex, age, clinical or subclinical condition and anti TPO were not correlate with weight change.Conclusion: According to our results less than fifty percent of hypothyroid patients lost weight after levothyroxine therapy. Subjects with higher basal weight, BMI and TSH had more weight loss.