title: 131I treatment for thyroid cancer and risk of developing primary hyperparathyroidism: a cohort study.
abstract: OBJECTIVE
  To evaluate the association between (131)I therapy for thyroid cancer and risk of developing primary hyperparathyroidism.
  
  
  METHODS
  This was a nationwide population-based cohort study of patients with thyroid cancer diagnosed during the period 1997-2008. The data were obtained from the Taiwan National Health Insurance Research dataset. The cumulative (131)I dose in each patient was calculated. Hazard ratios (HRs) were calculated using a proportional hazards model to estimate the effect of (131)I therapy on the risk of developing primary hyperparathyroidism in the cohort.
  
  
  RESULTS
  A total of 8,946 patients with thyroid cancer were eligible for the final analysis. Among these patients, 8 developed primary hyperparathyroidism during the follow-up period that represented 38,248 person-years giving an incidence rate of 20.9 per 10(5) person-years. (131)I was used in the treatment of 6,153 patients (68.8%) with a median cumulative dose of 3.7 GBq. The adjusted HRs were 0.21 (95% CI 0.02-1.86) and 0.46 (95% CI 0.10-2.10) for those receiving a cumulative (131)I dose of 0.1-3.6 GBq and ≥3.7 GBq, respectively, compared to no therapy. The risk of developing primary hyperparathyroidism did not increase with increasing (131)I dose (test for trend p = 0.51). No interaction was found between (131)I dose and age (p = 0.94) or (131)I dose and sex (p = 0.99).
  
  
  CONCLUSIONS
  (131)I treatment for thyroid cancer did not increase risk of primary hyperparathyroidism during a 10-year follow-up in this study population. Further research with a longer follow-up period is needed to assess late adverse effects beyond 10 years.
authors: Department of Nuclear Medicine, Taipei Medical University - Shuang Ho Hospital, Taipei, Taiwan.
authors: Chien-Mu
authors: CM
authors: Lin
authors: Pat
authors: P
authors: Doyle
authors: Yu-Tse
authors: YT
authors: Tsan
authors: Chang-Hsing
authors: CH
authors: Lee
authors: Jung-Der
authors: JD
authors: Wang
authors: Pau-Chung
authors: PC
authors: Chen
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006961:Hyperparathyroidism / Q000209:etiology*; D007457:Iodine Radioisotopes / Q000009:adverse effects* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D019275:Radiopharmaceuticals / Q000009:adverse effects* / Q000627:therapeutic use; D013964:Thyroid Neoplasms / Q000532:radiotherapy*
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals
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