Endocrine Abstracts

Background: Patients who require levothyroxine (LT4) supplementation after total thyroidectomy often have difficulty achieving target TSH levels. Several studies have attempted to develop a dosing schedule considering different factors such as age, gender, weight, or body mass index (BMI) as potential determinants of the correct dose of LT4. The objective of this study is to determine if a scheme that uses the percentage of body fat (%BF) measured by CUN-BAE is more accurate to correctly predict levothyroxine dose requirements.

Methods: Data from 143 patients who underwent total thyroidectomy for benign and malignant disease at our institution between 1993 and 2021 were retrospectively reviewed. Two new dosing formulas, CUN-BAE Model 1 and CUN-BAE Model 2, were designed using Poisson’s regression. These dosing models were applied to our cohort and compared with other dosing schemes proposed in the literature. The accuracy of each model was established by determining the proportion of correct estimates.

Results: CUN-BAE-1 and CUN-BAE-2 accurately estimated 61.5% and 62.9% of LT4 doses, respectively. These results slightly improve the precision of previous methods such as the Poisson regression proposed by Zaborek et al based in several factors including BMI (estimated 60.1%) and the weight-based model (estimated 55.9%) of correct doses.

Conclusion: − The use of %BF calculated by the CUN-BAE formula to adjust the dose of LT4 after total thyroidectomy is a simple and accurate method that improves current formulas based on weight or BMI.