title: Systemic oxidative stress to nucleic acids is unaltered following radioiodine therapy of patients with benign nodular goiter.
abstract: BACKGROUND
  Little is known about the whole body oxidative stress burden following radioactive iodine ((131)I) therapy of thyroid diseases.
  
  
  METHODS
  We studied 17 patients with benign nodular goiter treated with (131)I therapy. The targeted thyroid dose was 50 Gy in 11 patients pretreated with 0.1 mg of recombinant human TSH (rhTSH). In 6 patients, the applied thyroid dose was 100 Gy without rhTSH prestimulation. Well-established biomarkers of oxidative stress to RNA (8-oxo-7,8-dihydroguanosine; 8-oxoGuo) and DNA (8-oxo-7,8-dihydro-2'-deoxyguanosine; 8-oxodG) were measured in freshly voided morning urine (normalized against the creatinine concentration) at baseline, and 7 and 21 days after rhTSH (not followed by (131)I), and 7 and 21 days after (131)I therapy, respectively.
  
  
  RESULTS
  The baseline urinary excretions of 8-oxoGuo and 8-oxodG were 2.20 ± 0.84 and 1.63 ± 0.70 nmol/mmol creatinine, respectively. We found no significant changes in the excretion of any of the metabolites, neither after rhTSH stimulation alone nor after (131)I therapy. Also, no significant differences were found between the rhTSH group (low dose, median (131)I: 152 MBq) and the non-rhTSH group (high dose, median (131)I: 419 MBq; 8-oxoGuo: p = 0.66, 8-oxodG: p = 0.71).
  
  
  CONCLUSIONS
  Systemic oxidative stress, as detected by nucleic acids metabolites in the urine, is not increased after thyroid stimulation with 0.1 mg of rhTSH, or after (131)I therapy. Our method cannot quantify the oxidative stress induced locally in the thyroid gland, but the study supports that (131)I therapy of benign nodular goiter carries no or only a minute risk of developing subsequent malignancies. It remains to be explored whether our findings also apply to hyperthyroid disorders.
authors.affiliation: Department of Endocrinology, Odense University Hospital, Odense, Copenhagen, Denmark.
authors.forename: Steen J
authors.initials: SJ
authors.lastname: Bonnema
authors.affiliation: Department of Laboratory of Clinical Pharmacology Q7642, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Elisabeth S
authors.initials: ES
authors.lastname: Stovgaard
authors.affiliation: Department of Endocrinology, Odense University Hospital, Odense, Copenhagen, Denmark.
authors.forename: Søren
authors.initials: S
authors.lastname: Fast
authors.affiliation: Department of Laboratory of Clinical Pharmacology Q7642, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Kasper
authors.initials: K
authors.lastname: Broedbaek
authors.affiliation: Department of Laboratory of Clinical Pharmacology Q7642, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Jon T
authors.initials: JT
authors.lastname: Andersen
authors.affiliation: Department of Laboratory of Clinical Pharmacology Q7642, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Allan
authors.initials: A
authors.lastname: Weimann
authors.affiliation: Department of Nuclear Medicine, Odense University Hospital, Odense, Copenhagen, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Grupe
authors.affiliation: Department of Endocrinology, Odense University Hospital, Odense, Copenhagen, Denmark.
authors.forename: Laszlo
authors.initials: L
authors.lastname: Hegedüs
authors.affiliation: Department of Laboratory of Clinical Pharmacology Q7642, Rigshospitalet, Copenhagen, Denmark ; Department of Clinical Pharmacology, Bispebjerg Hospital, Copenhagen, Denmark ; Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Henrik E
authors.initials: HE
authors.lastname: Poulsen
keywords: 8-oxo-7,8-dihydro-2’-deoxyguanosine; 8-oxo-7,8-dihydroguanosine; Goiter; Oxidative stress; Radioactive iodine; Recombinant human TSH