title: Testicular dose and fertility in men following I(131) therapy for thyroid cancer.
abstract: OBJECTIVE
  Young adults with differentiated thyroid cancer are treated with high doses of radioiodine and have an excellent long-term prognosis. However, there is limited information on the effects of this treatment on the gonads and fertility in male patients. We have reviewed the outcome of treatment in our centre with respect to male fertility. We have also assessed directly the radiation dose received by the testes.
  
  
  METHODS
  Retrospective analysis of males attending the thyroid clinic at the Royal Marsden Hospital for treatment of differentiated thyroid cancer. A prospective study was also performed to assess radiation dose to testes in 14 consecutive patients attending for thyroid cancer treatment.
  
  
  METHODS
  Males under the age of 40 years at the time of treatment with a minimum of 3 years follow-up.
  
  
  METHODS
  Number of children fathered by patients and number of congenital malformations. For the prospective study: gonadal function assessed by serum FSH, LH and testosterone measurements; radiation dose to the testes (Gy) measured by thermoluminescent dosimetry.
  
  
  RESULTS
  Fertility was assessed in 122 men with a median follow-up of 21 years (range 3-39) of whom 93 were under active follow-up. One hundred and six children were fathered by 59 patients; the remainder had no wish to have children. No major malformations were reported. Of these 59 patients, 12 had received a single 3 GBq ablation dose, 19 had been treated with up to 14 GBq radioiodine and 28 had received up to 44 GBq. In 14 patients followed prospectively, the median estimated radiation dose to each testis was 6.4 cGy following 3 GBq, 14.1 cGy following 5.5 GBq and 21.2 cGy following 9.2 GBq. There was a transient elevation in serum FSH after radioiodine which normalized within 9 months from the last administration.
  
  
  CONCLUSIONS
  Radioiodine treatment for thyroid cancer may result in transient impairment of gonadal function. The radiation dose absorbed by the testis after a single ablative dose of radioiodine is well below that associated with permanent damage to germinal epithelium and the risk of infertility in these patients is minimal. Patients requiring multiple administrations for persistent or metastatic thyroid cancer may be at greater risk of gonadal damage although even in this group, we found no evidence of infertility.
authors.affiliation: Thyroid Unit, Royal Marsden NHS Trust, Sutton, Surrey, UK. shyer@sthelier.sghms.ac.uk
authors.forename: Stephen
authors.initials: S
authors.lastname: Hyer
authors.forename: Louiza
authors.initials: L
authors.lastname: Vini
authors.forename: Mary
authors.initials: M
authors.lastname: O'Connell
authors.forename: Brenda
authors.initials: B
authors.lastname: Pratt
authors.forename: Clive
authors.initials: C
authors.lastname: Harmer
mesh_terms: D018249:Adenoma, Oxyphilic / Q000532:radiotherapy / Q000601:surgery; D000328:Adult; D002291:Carcinoma, Papillary / Q000532:radiotherapy / Q000601:surgery; D018265:Carcinoma, Papillary, Follicular / Q000532:radiotherapy / Q000601:surgery; D005298:Fertility / Q000528:radiation effects*; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D013737:Testis / Q000528:radiation effects*; D013964:Thyroid Neoplasms / Q000532:radiotherapy* / Q000601:surgery
chemical_list: D007457:Iodine Radioisotopes