title: Radioiodine therapy in patients with amiodarone-induced thyrotoxicosis (AIT).
abstract: BACKGROUND
  Amiodarone (AM) is frequently used in the therapy of patients with cardiac disorders. However, due to high iodine content, it has side effects on thyroid function. The use of radioiodine therapy (RIT) in amiodarone-induced thyrotoxicosis (AIT) with low radioactive iodine uptake (RAIU) is still controversial. In these patients therapeutic choices for refractory disease include surgery, antithyroid drugs, or glu ocorticosteriods.
  
  
  OBJECTIVE
  The aim of the study was to evaluate the efficacy of RIT in patients presenting AIT and low RAIU in two-year follow-up.
  
  
  METHODS
  40 patients (25 men and 15 women) aged from 63 to 83 years (x +/- SD: 66.2 +/- 5.0 years; median: 65 years) treated with RIT were included into the study. In these patients AM therapy was essential for the underlying heart disorder, while surgery, antithyroid drugs or glucocorticosteroids, were contraindicated. Forty seven patients with toxic multinodular goiter (TMNG) (39 women and 8 men), matched for age (67 +/- 12 yr; range 54-89 yr), were enrolled into the study as a comparative group. The diagnostic procedures included baseline thyroid function tests (thyrothropin - TSH, free triiodothyronine - fT3 and free thyroxine - fT4 levels), thyroid autoantibodies measurement (antithyroglobulin autoantibodies - TgAb, antithyroid peroxidase autoantibodies - TPOAb, anti-TSH receptor autoantibodies - TRAb), thyroid ultrasonography, thyroid scintiscan and RAIU assessment.
  
  
  RESULTS
  Serum values of TSH, TgAb, TPOAb and TRAb were undetectable in both groups. In patients with AIT fT4 level was 18.7 to 38.7 pmol/l (mean: 27.1 +/- 5.8) and fT3 concentration was 3.9 to 5.6 pmo/l (mean: 5.7 +/- 1.4), while in TMNG patients level of fT4 was 31.5 to 22.2 pmol/l (mean: 25,3 +/- 5,8) and fT3 concentration was 3.8 to 4,2 pmo/l (mean: 4,2 +/- 0,2). Mean RAIU values after 5h and 24h in AIT patients were 2.3 +/- 0.5 and 3.1 +/- 0.9%, while in TMNG patients were 18,0 +/- 3,8 and 35,7 +/- 9,1%, respectively. A significant difference (p<0.001) between 5h and 24h RAIU in AIT compared to TMNG was noted. In all patients with AIT, a dose of 800 MBq of 131I was administered. During two-year-observation recurrence of hyperthyroidism was observed in two patients (5%) with TMNG. These patients received a second radioiodine dose 16.2 +/- 15 months later (the mean re-treatment dose was 735.93 +/- 196.1 MBq). In comparison, none of the patients with AIT required a second 131I dose and only one patient (2.5%) 6 months after ablative 131I dose needed anti-thyroid medication. Transient hypothyroidism was observed in only two patients (5%) with AIH, though was not observed in TMNG. During follow-up time, no sudden deaths in AIT patients were observed; one patient was diagnosed with prostate cancer, and in one patient acute toxic hepatitis after AM occurred.
  
  
  CONCLUSIONS
  RIT may be a safe and useful method of AIT therapy in patients with low RAIU, in whom other treatment methods are contraindicated.
authors.affiliation: Department of Endocrinology, Metabolism and Internal Medicine, Poznan University of Medical Sciences, Poland. agata.rat@wp.pl
authors.forename: Agata
authors.initials: A
authors.lastname: Czarnywojtek
authors.forename: Rafal
authors.initials: R
authors.lastname: Czepczynski
authors.forename: Marek
authors.initials: M
authors.lastname: Ruchala
authors.forename: Ryszard
authors.initials: R
authors.lastname: Wasko
authors.forename: Magorzata
authors.initials: M
authors.lastname: Zgorzalewicz-Stachowiak
authors.forename: Ewelina
authors.initials: E
authors.lastname: Szczepanek
authors.forename: Hanna
authors.initials: H
authors.lastname: Zamyslowska
authors.forename: Zuzanna
authors.initials: Z
authors.lastname: Bartkowiak
authors.forename: Ewa
authors.initials: E
authors.lastname: Florek
authors.forename: Jerzy
authors.initials: J
authors.lastname: Sowinski
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000638:Amiodarone / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006042:Goiter / Q000532:radiotherapy; D006801:Humans; D007037:Hypothyroidism / Q000139:chemically induced; D007457:Iodine Radioisotopes / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D012074:Remission Induction; D013971:Thyrotoxicosis / Q000139:chemically induced* / Q000532:radiotherapy*; D013997:Time Factors; D016896:Treatment Outcome; D014665:Vasodilator Agents / Q000009:adverse effects*
chemical_list: D007457:Iodine Radioisotopes; D014665:Vasodilator Agents; D000638:Amiodarone