Objectives: To study the influencing factors of levothyroxine (L-T4) dose in patients with hypothyroidism in real world and establish a predictive model of the daily dose of L-T4.

Methods: A cross-sectional survey was conducted, screening for patients with hypothyroidism randomly. The patient’s basic information, such as age, gender, weight, Body mass index(BMI),the history of female menopause, causes and duration of hypothyroidism, and serum concentration of thyroid hormones and related antibodies were causal variables; the daily dose of L-T4 was used as outcome variable. We studied the key factors that may influence the outcome variables, and used the multiple linear regression techniques to establish a patient L-T4 dose prediction model.

Results: Factors that may affect L-T4 dose in patients include age(P<0.001),hypothyroidism duration (P=0.001),causes of hypothyroidism(P=0.036), serum free triiodothyronine(FT3) concentration(P<0.001) and serum free thyroxine(FT4) concentration(P <0.001). After using the stepwise method for variable screening, the L-T4 dose predictive model for hypothyroidism patients was: the daily dose of L-T4=63.98-0.43*age+0.76*hypothyroidism duration+4.68* causes of hypothyroidis-9.85*serum FT3 concentration+3.39*serum FT4 concentration, R=0.557. The predicted residual is distributed within 2 standard deviations.

Conclusions: Record the patient’s age, the cause and duration of hypothyroidism, and measure the serum FT3 and FT4 concentrations to help predict the daily dose of L-T4 in patients with hypothyroidism in the real world; the established L-T4 dose prediction model has certain predictive performance, which can provide reference for optimal oral dose of L-T4 in hypothyroidism patients.