title: Outcome of radioiodine-131 therapy in hyperfunctioning thyroid nodules: a 20 years' retrospective study.
abstract: OBJECTIVE
  To investigate the risk of hypothyroidism after radioiodine (131I) treatment for hyperfunctioning thyroid nodules.
  
  
  METHODS
  Retrospective analysis of patients treated with 131I for hyperfunctioning thyroid nodules and followed up for a maximum of 20 years.
  
  
  METHODS
  A total of 346 patients treated with 131I in the years 1975-95, for a single hyperfunctioning nodule.
  
  
  METHODS
  Hypothyroidism was defined as TSH levels > 3.7 mU/l. Kaplan-Meier survival analysis was used to analyse permanence of euthyroidism after 131I. A stepwise Cox proportional hazard model was used to identify factors influencing the progression to hypothyroidism.
  
  
  RESULTS
  The cumulative incidence of hypothyroidism was 7.6% at 1 year, 28% at 5 years, 46% at 10 years and 60% at 20 years. Age (P < 0.01), 24-th 131I uptake (P < 0.05) and previous treatment with methimazole (MMI, P < 0.1) were associated with a faster progression towards hypothyroidism, while thyroid and nodule size, thyroid status at diagnosis and degree of extranodular thyroid parenchymal suppression had no influence. In hyperthyroid patients with partial parenchymal suppression, however, previous MMI treatment was the most important prognostic factor (P < 0.01).
  
  
  CONCLUSIONS
  After 20 years of follow-up, 60% of patients treated with 131I for a single hyperfunctioning nodule are hypothyroid. Factors increasing the risk of hypothyroidism are age, 131I uptake and MMI pretreatment. The prognostic value of this last factor, however, depends on the degree of suppression of the extranodular thyroid parenchyma at the scan.
authors.affiliation: Department of Endocrinology, University of Pisa, Opsedale Cisanello, Pisa, Italy. claudiac@endoc.med.unipi.it
authors.forename: Claudia
authors.initials: C
authors.lastname: Ceccarelli
authors.forename: Walter
authors.initials: W
authors.lastname: Bencivelli
authors.forename: Paolo
authors.initials: P
authors.lastname: Vitti
authors.forename: Lucia
authors.initials: L
authors.lastname: Grasso
authors.forename: Aldo
authors.initials: A
authors.lastname: Pinchera
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D013956:Antithyroid Agents / Q000009:adverse effects; D018450:Disease Progression; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000532:radiotherapy*; D007037:Hypothyroidism / Q000209:etiology; D007457:Iodine Radioisotopes / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D008713:Methimazole / Q000009:adverse effects; D008875:Middle Aged; D011832:Radiation Injuries / Q000209:etiology; D013961:Thyroid Gland / Q000502:physiology; D016606:Thyroid Nodule / Q000532:radiotherapy*; D013972:Thyrotropin / Q000097:blood; D016896:Treatment Outcome
chemical_list: D013956:Antithyroid Agents; D007457:Iodine Radioisotopes; D008713:Methimazole; D013972:Thyrotropin