title: Determinants and outcome of amiodarone-associated thyroid dysfunction.
abstract: OBJECTIVE
  Amiodarone is frequently associated with thyroid dysfunction. Identifying predictors for amiodarone-associated thyroid dysfunction and assessing treatment outcome may aid clinicians in daily practice.
  
  
  METHODS
  We included 303 consecutive patients with amiodarone therapy for cardiac arrhythmias (260 with atrial fibrillation and 43 with ventricular arrhythmias). Thyroid function tests were performed every 6 months.
  
  
  RESULTS
  Mean age was 63 ± 12 years and 66% was male. After median follow-up of 3·3 (0·1-24) years, 23 (8%) patients developed amiodarone-associated thyrotoxicosis (incidence rate 1·9 per 100 person years) and 18 (6%) hypothyroidism (incidence rate 1·1 per 100 person years). The only predictor for amiodarone-associated thyrotoxicosis was age <62 years [HR = 2·4 (95% CI 1·0-5·7), P = 0·05]. Predictors for amiodarone-associated hypothyroidism were thyroid stimulating hormone >1·4 mU/l at baseline [HR = 5·1 (95% CI 1·1-22·4), P = 0·03], left ventricular ejection fraction <45% [HR = 3·8 (95% CI 1·1-13·3), P = 0·04] and diabetes mellitus at baseline [HR = 3·3 (95% CI 1·1-10·3), P = 0·04]. Gender was not a predictor for amiodarone-associated thyroid dysfunction. Five out of 12 (42%) patients with thyrotoxicosis exhibited spontaneous normalization of thyroid function on continuation of amiodarone therapy. Mean time to normalization in the total group was 6·2 ± 3·3 months, with no difference between continuing or discontinuing amiodarone (6·6 ± 3·8 vs 5·8 ± 2·8 months, P = 0·5).
  
  
  CONCLUSIONS
  During median follow-up of 3·3 years, the incidence of amiodarone-associated thyrotoxicosis was higher compared to hypothyroidism. Only general predictors for amiodarone-associated thyroid dysfunction were observed. Discontinuation of amiodarone did not influence treatment outcome.
authors.affiliation: Department of Cardiology, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Sheba
authors.initials: S
authors.lastname: Ahmed
authors.forename: Isabelle C
authors.initials: IC
authors.lastname: Van Gelder
authors.forename: Ans C P
authors.initials: AC
authors.lastname: Wiesfeld
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: Van Veldhuisen
authors.forename: Thera P
authors.initials: TP
authors.lastname: Links
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000638:Amiodarone / Q000009:adverse effects* / Q000627:therapeutic use; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects / Q000627:therapeutic use; D001145:Arrhythmias, Cardiac / Q000188:drug therapy* / Q000503:physiopathology; D016208:Databases, Factual / Q000706:statistics & numerical data; D003920:Diabetes Mellitus / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007037:Hypothyroidism / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology*; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012189:Retrospective Studies; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000378:metabolism / Q000503:physiopathology; D013971:Thyrotoxicosis / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology*; D013972:Thyrotropin / Q000378:metabolism; D016896:Treatment Outcome
chemical_list: D000889:Anti-Arrhythmia Agents; D013972:Thyrotropin; D000638:Amiodarone