title: The Cut-Off Level of Recombinant Human TSH-Stimulated Thyroglobulin in the Follow-Up of Patients with Differentiated Thyroid Cancer.
abstract: BACKGROUND
  The treatment of differentiated thyroid cancer (DTC) ends in full recovery in 80% of cases. However, in 20% of cases local recurrences or distant metastases are observed, for this reason DTC patients are under life-long follow-up. The most sensitive marker for recurrence is stimulated thyroglobulin (Tg) which, together with neck ultrasound (US), enables correct diagnosis in nearly all cases of the active disease. For many years the only known stimulation was a 4-5 week withdrawal from the L-T4 therapy (THW). For the last couple of years stimulation with the use of recombinant human TSH (rhTSH) has been available. This method of stimulation may have a significant influence in obtaining the Tg level. However, it is important to determine the cut-off level for rhTSH-stimulated Tg (rhTSH/Tg).
  
  
  METHODS
  This is a retrospective analysis of consecutive patients from one facility who have qualified over a period of two years for repeated radioiodine therapy (RIA). In our facility the ablation effectiveness evaluation is always carried out with the use of rhTSH, with the repeated therapy following THW. Such a procedure enables two Tg measurements in the same patient after both types of stimulation within 4-5 weeks. The obtained values were compared, cut-off levels in THW conditions were used (2.0 ng/ml for patients in remission and 10.0 ng/ml for patients with an active disease). In order to determine the cut-off level for rhTSH/Tg, regression analysis and ROC curves were used.
  
  
  RESULTS
  In 63 patients the Tg measurement of both methods of stimulation were obtained. It was observed that there was a high correlation between rhTSH/Tg and THW/Tg. However, the rhTSH/Tg level was significantly lower than THW/ Tg. The rhTSH/ Tg cut-off levels which corresponded to the 2.0 ng/ml and 10.0 ng/ml limits for THW/Tg were calculated and the values were 0.6 ng/ml and 2.3 ng/ml respectively.
  
  
  CONCLUSIONS
  The method of stimulation has a significant impact on the obtained Tg concentrations. The assumed THW/Tg cut off levels must not be transferred to rhTSH/Tg.
authors.affiliation: Endocrinology Department, Holycross Cancer Centre, Kielce, Poland.
authors.forename: Aldona
authors.initials: A
authors.lastname: Kowalska
authors.affiliation: Endocrinology Department, Holycross Cancer Centre, Kielce, Poland.
authors.forename: Iwona
authors.initials: I
authors.lastname: Pałyga
authors.affiliation: Endocrinology Department, Holycross Cancer Centre, Kielce, Poland.
authors.forename: Danuta
authors.initials: D
authors.lastname: Gąsior-Perczak
authors.affiliation: Endocrinology Department, Holycross Cancer Centre, Kielce, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Walczyk
authors.affiliation: Endocrinology Department, Holycross Cancer Centre, Kielce, Poland.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Trybek
authors.affiliation: Laboratory of Tumor Markers, Holycross Cancer Centre, Kielce, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Słuszniak
authors.affiliation: Endocrinology Department, Holycross Cancer Centre, Kielce, Poland.
authors.forename: Ryszard
authors.initials: R
authors.lastname: Mężyk
authors.affiliation: Clinical Oncology Department, Holycross Cancer Centre, Kielce, Poland.
authors.forename: Stanisław
authors.initials: S
authors.lastname: Góźdź
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism*; D012189:Retrospective Studies; D013954:Thyroglobulin / Q000378:metabolism*; D013960:Thyroid Function Tests / Q000379:methods; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000532:radiotherapy; D013972:Thyrotropin / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D013972:Thyrotropin; D013954:Thyroglobulin