Individual Dosing of Levothyroxine After Thyroidectomy

Compare a New Method to the Traditional One to Estimate Levothyroxine Dose for Patients Needing Replacement Therapy After Total or Completion Thyroidectomy

Recently, Zaborek et al. raised a Poisson regression model for levothyroxine(LT4) dosing scheme to predict individual dose of LT4 after thyroidectomy: daily LT4 dose=e[2.02+0.01(W)-0.0037(A )-0.098(F)-0.01(B)+0.007(T)+0.108(I)-0.014(M), where W is the weight of the patient (Kg), A is the age of the patient (years), and F is the gender (for women 1, male is 0), B represents the patient's body mass index (BMI), T represents the preoperative TSH level, I represents whether the patient takes iron preparations (1, if not 0), M represents whether the patient takes multivitamins/minerals (1, if not 0). We demonstrated its value with our retrospective data in our center. Therefore, we intend to carry out this randomized controlled trial in order to further evaluate the model. The clinical significance of this method can provide a basis for the future use in clinical optimization of individualized dosing.

Patients who underwent total/near-total thyroidectomy or completion thyroidectomy and require levothyroxine replacement therapy will be enrolled in this study. They will be randomized distributed into two groups. In one group, patients will be dosing LT4 according to weight-based algorithm, namely 1.6 μg /kg/d. In the other group, patients will be dosing LT4 according to the Poisson regression model algorithm. They will be followed up 3-6 weeks after surgery for the first time. During the follow up, thyroid hormone will be tested and LT4 dosing will be adjusted accordingly. Then, we compare patients in which group will achieve euthyroidism more quickly.

levothyroxine, thyroidectomy, thyroid hormone replacement therapy, individualized therapy, regression model

daily levothyroxine dose=e[2.02+0.01(W)-0.0037(A )-0.098(F)-0.01(B)+0.007(T)+0.108(I)-0.014(M), where W is the weight of the patient (Kg), A is the age of the patient (years), and F is the gender (for women 1, male is 0), B represents the patient's body mass index (BMI), T represents the preoperative TSH level, I represents whether the patient takes iron preparations (1, if not 0), M represents whether the patient takes multivitamins/minerals (1, if not 0).

For patients in experimental group, initial levothyroxine dose is calculated through the Poisson regression model; and for patients in comparator group, initial levothyroxine dose is calculated through 1.6 ug/kg/d.

Inclusion Criteria: patients underwent total/near-total thyroidectomy or completion thyroidectomy; patients with benign disease, or low-risk differentiated thyroid cancer, or medullary thyroid cancer who don't need TSH suppressive therapy; Exclusion Criteria: patients with heart disease or severe liver/kidney insufficiency; patients taking liothyronine in addition to levothyroxine;

Zaborek NA, Cheng A, Imbus JR, Long KL, Pitt SC, Sippel RS, Schneider DF. The optimal dosing scheme for levothyroxine after thyroidectomy: A comprehensive comparison and evaluation. Surgery. 2019 Jan;165(1):92-98. doi: 10.1016/j.surg.2018.04.097. Epub 2018 Nov 6. Erratum In: Surgery. 2022 Jul;172(1):477.