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Erciyes Medical Journal Levothyroxine Dosage Determination According to Body Mass Index (BMI) After Total Thyroidectomy [Erciyes Med J]
Erciyes Med J. 2019; 41(2): 196-200 | DOI: 10.14744/etd.2019.14892

Levothyroxine Dosage Determination According to Body Mass Index (BMI) After Total Thyroidectomy

Hemmat Maghsoudi1, Seyed Ehsan Mousavi Toomatari1, Naser Agha Mohammadzade2, Farzad Najafipour2, Sara Akhavan Salamat3, Seyed Babak Moosavi Toomatari4, Afshin Gharekhani5
1Department of General Surgery, Imam Reza Hospital, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
2Endocrine Research Center, Tabriz University of Medical Science, Tabriz, Iran
3Department of Anesthesiology, Imam Reza Hospital, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
4Department of General Surgury, Zanjan University of Medical Sciences, Zanjan, Iran
5Department of Pharmacy, Sina Hospital, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran

Objective: Currently, postoperative thyroid hormone replacement dosing is weight-based with adjustments and made following Thyroid Stimulating Hormone (TSH) values, which may lead to delayed achievement of euthyroidism and failure in achieving an accurate estimation of the levothyroxine dose. We aimed to evaluate the relationship between Body Mass Index (BMI) and Lean Body Mass (LBM) with levothyroxine dose.
Materials and Methods: Eighty patients with thyroid disease (benign and malignant) randomly enrolled the study. BMI and LBM were calculated during the pre-operative visit. Thyroid hormone replacement was started five day after surgery for benign and after a month for malignant cases, at a dose of 1.6 mcg/kg/day based on actual body weight. When euthyroidism was achieved, the levothyroxine dose was measured, and efforts were made to analyze its relationship with weight, BMI, and LBM.
Results: In the benign group, levothyroxine dose was obtained at 1.51 mcg/kg per body weight. To determine the levothyroxine dose based on BMI and LBM, Y=–0.013+0.005 BMI and Y=0.048+0.002 LBM formulas were used, respectively. In the malignant group, a levothyroxine dose of 1.56 mcg/kg was obtained based on the weight variable. To determine the levothyroxine dose based on BMI and LBM, Y=0.01+0.004 BMI and Y=0.042+0.002 LBM formulas were used, respectively. In both groups, the levothyroxine dose that was calculated was more accurate using BMI with the obtained formula.
Conclusion: Weight, BMI, and LBM can be used to determine the levothyroxine dose in patients receiving total thyroidectomy, but levothyroxine can be precisely measured using BMI.

Keywords: Levothyroxine, total thyroidectomy, BMI

Hemmat Maghsoudi, Seyed Ehsan Mousavi Toomatari, Naser Agha Mohammadzade, Farzad Najafipour, Sara Akhavan Salamat, Seyed Babak Moosavi Toomatari, Afshin Gharekhani. Levothyroxine Dosage Determination According to Body Mass Index (BMI) After Total Thyroidectomy. Erciyes Med J. 2019; 41(2): 196-200

Corresponding Author: Seyed Ehsan Mousavi Toomatari, Iran
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