Levothyroxine dose according to body weight in patients with severe subclinical hypothyroidism

Introduction: The dosage of levothyroxine can be determined based on a patient's weight and is estimated to be 1.6 to 2.1 mcg/kg/day for primary hypothyroidism. This study aimed to determine the mean weight-based dose of thyroxine in patients with severe subclinical hypothyroidism. Methods: Patients with TSH values between 10 and 20 mIU/mL and normal fT4 levels who achieved euthyroid status were retrospectively analyses. A total of 51 patients were included in the study. Results: The mean age was 58.11 ±17.4 years, and the mean weight was 74.78±15.9 kg. Females were 86%. The mean dose of levothyroxine to achieve euthyroid status was 72.40 ± 25.5 mcg/day, or 0.996± 0.35 mcg/kg/day. The mean TSH level after treatment was 2.621±1.22 mU/L. Age, gender, height, and disease duration did not impact achieving a euthyroid state (p>0.05). Conclusion: Determining the correct levothyroxine dosage involves more than a simple weight-based calculation. However, understanding the mean dose relative to weight allows healthcare providers to better tailor therapy to individual patient needs, improving outcomes, minimizing frequent visits, and reducing the risk of under- or over-treatment. Keywords. Subclinical hypothyroidism, weight-based calculation, levothyroxine.