title: Comparison of iodine uptake in tumour and nontumour tissue under thyroid hormone deprivation and with recombinant human thyrotropin in thyroid cancer patients.
abstract: OBJECTIVE
  Recombinant human thyrotropin (rhTSH) is a new option for diagnostic follow-up in patients with differentiated thyroid cancer (DTC). Iodine kinetics after administration of rhTSH is controversially discussed. The aim of our study was to compare the time course of radioiodine in tumour and normal tissue during periods of TSH elevation in patients in a hypothyroid state (HS) following hormone withdrawal, with those under euthyroidism (ES) after the administration of rhTSH.
  
  
  METHODS
  We investigated four patients who had undergone near-total thyroidectomy and were suffering from metastatic disease. Dosimetric calculations were performed using tumour and whole-body uptake, and background measurements from 123-iodine scans performed 0, 4, 24 and 48 h after the application of (123)I.
  
  
  RESULTS
  All patients had lesser uptake of (123)I under rhTSH stimulation than after hormone withdrawal. The median maximum TG (thyroglobulin) levels were 733.1 ng/ml with HS and 548.0 ng/ml with ES. The median half-life in tumour tissue was 39.8 h (mean 65.9, range 11.5-194.0) with HS and 21.9 h (mean 38.7, range. 8.7-113.9) with ES. The median uptake dose in per cent in tumour tissue was 0.08 (mean 0.15, range 0.04-0.6) with HS and 0.05 (mean 0.08, range 0.03-0.2) with ES. Furthermore, the cumulative activity in metastatic tissue was lower after rhTSH than during hypothyroidism, with considerable variations between individual lesions.
  
  
  CONCLUSIONS
  In our small group of DTC patients with metastatic disease, the effectiveness of radioiodine therapy following rhTSH was anticipated to be less than that in individuals who were hypothyroid after levothyroxine (L-T(4)) withdrawal. Endogenous TSH stimulation of metastatic thyroid cancer with radioiodine should not be performed without prior target tumour lesion dosimetry with (123)I.
authors.affiliation: Department of Nuclear Medicine, Medical University of Vienna, Austria. christian.poetzi@meduniwien.ac.at
authors.forename: Christian
authors.initials: C
authors.lastname: Pötzi
authors.forename: Abbas
authors.initials: A
authors.lastname: Moameni
authors.forename: Georgios
authors.initials: G
authors.lastname: Karanikas
authors.forename: Josef
authors.initials: J
authors.lastname: Preitfellner
authors.forename: Alexander
authors.initials: A
authors.lastname: Becherer
authors.forename: Christian
authors.initials: C
authors.lastname: Pirich
authors.forename: Robert
authors.initials: R
authors.lastname: Dudczak
mesh_terms: D000369:Aged, 80 and over; D001323:Autoantibodies / Q000097:blood; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D011874:Radiometry / Q000379:methods; D011994:Recombinant Proteins / Q000627:therapeutic use; D018709:Statistics, Nonparametric; D013954:Thyroglobulin / Q000097:blood / Q000276:immunology; D013964:Thyroid Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin / Q000627:therapeutic use*; D013974:Thyroxine / Q000627:therapeutic use
chemical_list: D001323:Autoantibodies; D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D013972:Thyrotropin; D013954:Thyroglobulin; D013974:Thyroxine