title: Clinical experience of amiodarone-induced thyrotoxicosis over a 3-year period: role of colour-flow Doppler sonography.
abstract: OBJECTIVE
  Current thinking is that amiodarone-induced thyrotoxicosis (AIT) might be either iodine-induced thyrotoxicosis in latent hyperthyroidism (Type 1) or destructive thyroiditis (Type 2), and also that colour-flow Doppler sonography (CFDS) of the thyroid and serum interleukin 6 (IL-6) are tools that can classify AIT and direct treatment. To assess the validity of this thinking, our objective was to determine whether CFDS and IL-6 identified AIT subgroups with distinct features.
  
  
  METHODS
  Retrospective case-note audit of all patients presenting with AIT to the Endocrine Department of a UK teaching hospital over a 3-year period. To assess proportions of Type 1 vs. Type 2 AIT and to compare and contrast their clinical features.
  
  
  METHODS
  37 patients were identified with AIT (mean age 65, range 20-86 years). In 30 patients in whom AIT persisted, 25 underwent CFDS.
  
  
  RESULTS
  In 25 patients who underwent CFDS, 10 (40%) were classified as Type 1, 10 (40%) as Type 2 and 5 (20%) as indeterminate type. In the patients classified by CFDS in whom AIT persisted, 40% of Type 1 patients were male vs. 90% of Type 2 patients. Also, free T4 tended to be lower in patients presenting with Type 1 AIT (52.1 +/- 7.5 pmol/l) compared to Type 2 (74.8 +/- 8.1 pmol/l, P = 0.08), free T3 was lower (8.8 +/- 0.9 vs. 15.6 +/- 3.0 pmol/l, P = 0.03) and the cumulative amiodarone dose was lower (66 +/- 20 vs. 186 +/- 28 g, P = 0.002). We used less prednisolone to achieve euthyroidism in patients with Type 1 AIT whereas carbimazole doses were not different and the time to euthyroidism was the same in both groups (81 +/- 21 vs. 88 +/- 13 days). IL-6 was raised in two patients with Type 1 and in one patient with Type 2 AIT.
  
  
  CONCLUSIONS
  CFDS could characterize two distinct subtypes in patients with AIT. Conversely, IL-6 seemed to be an unhelpful test in this context.
authors.affiliation: Department of Endocrinology, Northern General Hospital, Sheffield, UK.
authors.forename: S E M
authors.initials: SE
authors.lastname: Eaton
authors.forename: H A
authors.initials: HA
authors.lastname: Euinton
authors.forename: C M
authors.initials: CM
authors.lastname: Newman
authors.forename: A P
authors.initials: AP
authors.lastname: Weetman
authors.forename: W M
authors.initials: WM
authors.lastname: Bennet
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000638:Amiodarone / Q000009:adverse effects*; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects*; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use; D013956:Antithyroid Agents / Q000627:therapeutic use; D002231:Carbimazole / Q000627:therapeutic use; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011239:Prednisolone / Q000627:therapeutic use; D012189:Retrospective Studies; D013971:Thyrotoxicosis / Q000139:chemically induced* / Q000175:diagnosis* / Q000188:drug therapy; D018615:Ultrasonography, Doppler, Color
chemical_list: D000889:Anti-Arrhythmia Agents; D000893:Anti-Inflammatory Agents; D013956:Antithyroid Agents; D015850:Interleukin-6; D002231:Carbimazole; D011239:Prednisolone; D000638:Amiodarone