title: Body mass index and the development of amiodarone-induced thyrotoxicosis in adults with congenital heart disease--a cohort study.
abstract: BACKGROUND
  Amiodarone-induced thyrotoxicosis (AIT) is a recognized complication of amiodarone treatment with limited management options. Its predisposing factors are incompletely defined yet a higher prevalence was reported in adults with congenital heart disease (CHD). Therefore we sought to determine the incidence and risk factors for AIT in adults with CHD.
  
  
  METHODS
  At a tertiary care center we followed a historical cohort of amiodarone-treated CHD patients for the period 1987-2009. Follow-up concluded at AIT diagnosis or with last thyroid assessment on amiodarone. Cumulative incidence of AIT was calculated. AIT association with nutritional status was hypothesized a priori.
  
  
  RESULTS
  AIT developed in 23/169 patients or 13.6%. The AIT incidence peaked in the 3rd year at 7.7%. AIT patients had a lower body mass index (BMI) at AMIO initiation compared with the rest of the cohort (mean ± standard deviation: 21.9 ± 2.9 vs. 25.1 ± 5.0; p<0.001). Patients with BMI<21 were more likely to develop thyrotoxicosis (RR=6.1) compared to those with BMI>25 (p<0.001). Presence of goiter was strongly associated with AIT (RR 3.6, p=0.002). Affected patients had a trend for higher cyanotic heart disease prevalence (34.8% vs. 17.8%, p=0.059). On multivariate analysis body mass index and goiter remained independent predictors of outcome.
  
  
  CONCLUSIONS
  BMI<21 at initiation of amiodarone therapy and presence of goiter are strong predictors of AIT in this population. Its incidence is time dependent. These predictors can be used clinically in assessing overall impact of amiodarone therapy in congenital heart disease patients.
authors.affiliation: Department of Internal Medicine, Division of Endocrinology, Mayo Clinic, Rochester, MN 55905, United States. stan.marius@mayo.edu
authors.forename: Marius N
authors.initials: MN
authors.lastname: Stan
authors.forename: Naser M
authors.initials: NM
authors.lastname: Ammash
authors.forename: Carole A
authors.initials: CA
authors.lastname: Warnes
authors.forename: Michael D
authors.initials: MD
authors.lastname: Brennan
authors.forename: Prabin
authors.initials: P
authors.lastname: Thapa
authors.forename: Michael R
authors.initials: MR
authors.lastname: Nannenga
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Bahn
mesh_terms: D000328:Adult; D000638:Amiodarone / Q000009:adverse effects*; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects; D015992:Body Mass Index; D015331:Cohort Studies; D016208:Databases, Factual / Q000639:trends; D005260:Female; D005500:Follow-Up Studies; D006330:Heart Defects, Congenital / Q000188:drug therapy* / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends; D063128:Tertiary Health Care; D013971:Thyrotoxicosis / Q000139:chemically induced* / Q000175:diagnosis / Q000453:epidemiology*; D055815:Young Adult
chemical_list: D000889:Anti-Arrhythmia Agents; D000638:Amiodarone