title: Proportion of type 1 and type 2 amiodarone-induced thyrotoxicosis has changed over a 27-year period in Italy.
abstract: BACKGROUND
  Two main forms of amiodarone-induced thyrotoxicosis (AIT) exist. Type 1 AIT is a form of iodine-induced hyperthyroidism. Its management is complex and includes thionamides, potassium perchlorate and, occasionally, thyroidectomy. Type 2 AIT is a destructive thyroiditis, responds to glucocorticoids, and usually does not require further thyroid treatment once euthyroidism has been restored.
  
  
  OBJECTIVE
  To assess retrospectively the prevalence and relative proportion of type 1 and type 2 AIT over a 27-year period at a tertiary referral centre in Italy.
  
  
  METHODS
  Consecutive AIT patients (n = 215) seen at the department of endocrinology of the University of Pisa between 1980 and 2006.
  
  
  RESULTS
  Type 1 AIT constituted the most frequent AIT form (60%) during the first years covered by this study. The annual mean number of type 1 AIT patients was 3.6 at the beginning of the study period, and 2.5 during the later years. In contrast, the mean annual number of new cases of type 2 AIT progressively increased from 2.4 to 12.5. Likewise, the proportion of type 2 AIT increased in a significant linear manner (P < 0.0001), currently accounting for 89% of AIT cases. Type 2 AIT patients showed a male preponderance, higher serum FT4/FT3 ratio (P < 0.002), lower 3-h and 24-h thyroidal radioactive iodine uptake values (P < 0.0001), and received a higher cumulative dose of amiodarone (P < 0.0001) than type 1 AIT patients.
  
  
  CONCLUSIONS
  Over a 27-year period, the epidemiology of AIT changed, as the prevalence of type 2 AIT progressively increased and that of type 1 remained constant. Thus, under most circumstances, endocrinologists nowadays deal with type 2 AIT, which is a destructive thyroiditis, generally treated successfully with glucocorticoids. Although no additional treatment is usually required after the destructive process subsides, periodic assessment of thyroid function is warranted, because of the occurrence of hypothyroidism (up to 17%) during long-term follow-up of these patients.
authors.affiliation: Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy. f.bogazzi@endoc.med.unipi.it
authors.forename: Fausto
authors.initials: F
authors.lastname: Bogazzi
authors.forename: Luigi
authors.initials: L
authors.lastname: Bartalena
authors.forename: Enrica
authors.initials: E
authors.lastname: Dell'Unto
authors.forename: Luca
authors.initials: L
authors.lastname: Tomisti
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rossi
authors.forename: Pasquale
authors.initials: P
authors.lastname: Pepe
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Tanda
authors.forename: Lucia
authors.initials: L
authors.lastname: Grasso
authors.forename: Enrico
authors.initials: E
authors.lastname: Macchia
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Aghini-Lombardi
authors.forename: Aldo
authors.initials: A
authors.lastname: Pinchera
authors.forename: Enio
authors.initials: E
authors.lastname: Martino
mesh_terms: D000368:Aged; D000638:Amiodarone / Q000009:adverse effects*; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects*; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000187:drug effects; D013971:Thyrotoxicosis / Q000139:chemically induced / Q000145:classification / Q000000981:diagnostic imaging / Q000453:epidemiology*; D018615:Ultrasonography, Doppler, Color
chemical_list: D000889:Anti-Arrhythmia Agents; D000638:Amiodarone