Real-world derived weight-based levothyroxine doses to achieve optimal thyrotropin target in different degrees of autoimmune hypothyroidism

Abstract

Abstract Purpose All patients with overt and severe subclinical hypothyroidism (SCH), and some with mild SCH require levothyroxine (L-T4) therapy. The present study aims to report real-world derived weight-based L-T4 doses to achieve optimal–low normal–thyrotropin target in different degrees of autoimmune hypothyroidism. Methods This was a retrospective study of patients with autoimmune hypothyroidism. Inclusion criteria were consistent achievement of optimal TSH target (0.3 to 2.5 µIU/L) using a stable L-T4 dose for at least 6 months. Patients were classified into 4 groups: group 1; mild SCH, group 2; severe SCH, group 3; overt hypothyroidism, and group 4; hypothyroidism with unknown initial TSH and free T4. Weight-based L-T4 doses were calculated for each group. Results Eighty-seven, 95, 75, and 91 patients met the inclusion criteria for groups 1–4, respectively. Weight-based L-T4 dose was the lowest in group 1 (1 ± 0.25 µg/kg/day), was the highest in group 3 (1.4 ± 0.29 µg/kg/day), while in groups 2 (1.2 ± 0.26 µg/kg/day), and 4 (1.2 ± 0.31 µg/kg/day) were not statistically different from each other. There was a significant decrease in weight-based L-T4 dose with increasing body weight categories in groups 1 and 2, and a significant difference between those less than 60 or ≥ 60 years of age in group 3. Conclusion Real-world derived weight-based L-T4 doses to achieve optimal TSH target are 1, 1.2, and 1.4 µg/kg/day for patients with mild, severe SCH, and overt autoimmune hypothyroidism, respectively. Age and body weight subcategories can better fine-tune required doses.