title: Using body mass index to predict optimal thyroid dosing after thyroidectomy.
abstract: BACKGROUND
  Current postoperative thyroid replacement dosing is weight based, with adjustments made after thyroid-stimulating hormone values. This method can lead to considerable delays in achieving euthyroidism and often fails to accurately dose over- and underweight patients. Our aim was to develop an accurate dosing method that uses patient body mass index (BMI) data.
  
  
  METHODS
  A retrospective review of a prospectively collected thyroid database was performed. We selected adult patients undergoing thyroidectomy, with benign pathology, who achieved euthyroidism on thyroid hormone supplementation. Body mass index and euthyroid dose were plotted and regression was used to fit curves to the data. Statistical analysis was performed using STATA 10.1 software (Stata Corp).
  
  
  RESULTS
  One hundred twenty-two patients met inclusion criteria. At initial follow-up, only 39 patients were euthyroid (32%). Fifty-three percent of patients with BMI >30 kg/m(2) were overdosed, and 46% of patients with BMI <25 kg/m(2) were underdosed. The line of best fit demonstrated an overall quadratic relationship between BMI and euthyroid dose. A linear relationship best described the data up to a BMI of 50. Beyond that, the line approached 1.1 μg/kg. A regression equation was derived for calculating initial levothyroxine dose (μg/kg/d = -0.018 × BMI + 2.13 [F statistic = 52.7, root mean square error of 0.24]).
  
  
  CONCLUSIONS
  The current standard of weight-based thyroid replacement fails to appropriately dose underweight and overweight patients. Body mass index can be used to more accurately dose thyroid hormone using a simple formula.
authors: Section of Endocrine Surgery, Department of Surgery, University of Wisconsin, Madison, WI 53792, USA.
authors: Kristin A
authors: KA
authors: Ojomo
authors: David F
authors: DF
authors: Schneider
authors: Alexandra E
authors: AE
authors: Reiher
authors: Ngan
authors: N
authors: Lai
authors: Sarah
authors: S
authors: Schaefer
authors: Herbert
authors: H
authors: Chen
authors: Rebecca S
authors: RS
authors: Sippel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015992:Body Mass Index; D001835:Body Weight; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011182:Postoperative Care; D012189:Retrospective Studies; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage* / Q000097:blood; D055815:Young Adult
chemical_list: D013972:Thyrotropin; D013974:Thyroxine