title: Does (131)I Radioactivity Interfere with Thyroglobulin Measurement in Patients Undergoing Radioactive Iodine Therapy with Recombinant Human TSH?
abstract: OBJECTIVE
  Recombinant human thyroid-stimulating hormone (rhTSH) is widely used in radioactive iodine therapy (RIT) to avoid side effects caused by hypothyroidism during the therapy. Owing to RIT with rhTSH, serum thyroglobulin (Tg) is measured with high (131)I concentrations. It is of concern that the relatively high energy of (131)I could interfere with Tg measurement using the immunoradiometric assay (IRMA). We investigated the effect of (131)I administration on Tg measurement with IRMA after RIT.
  
  
  METHODS
  A total of 67 patients with thyroid cancer were analysed retrospectively. All patients had undergone rhTSH stimulation for RIT. The patients' sera were sampled 2 days after (131)I administration and divided into two portions: for Tg measurements on days 2 and 32 after (131)I administration. The count per minute (CPM) of whole serum (200 μl) was also measured at each time point. Student's paired t-test and Pearson's correlation analyses were performed for statistical analysis.
  
  
  RESULTS
  Serum Tg levels were significantly concordant between days 2 and 32, irrespective of the serum CPM. Subgroup analysis was performed by classification based on the (131)I dose. No difference was noted between the results of the two groups.
  
  
  CONCLUSIONS
  IRMA using (125)I did not show interference from (131)I in the serum of patients stimulated by rhTSH.
authors.affiliation: Department of Nuclear Medicine, Seoul National University Bundang Hospital, 173-82, Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707 Republic of Korea ; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Sohyun
authors.initials: S
authors.lastname: Park
authors.affiliation: Department of Nuclear Medicine, Seoul National University Bundang Hospital, 173-82, Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707 Republic of Korea ; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Ji-In
authors.initials: JI
authors.lastname: Bang
authors.affiliation: Department of Nuclear Medicine, Seoul National University Bundang Hospital, 173-82, Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707 Republic of Korea ; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea ; Laboratory of Molecular Imaging and Therapy of Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Ho-Young
authors.initials: HY
authors.lastname: Lee
authors.affiliation: Department of Nuclear Medicine, Seoul National University Bundang Hospital, 173-82, Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707 Republic of Korea ; Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Sang-Eun
authors.initials: SE
authors.lastname: Kim
keywords: Immunoradiometric assay; Radioactive iodine therapy; Recombinant human TSH; Thyroglobulin