Urinary iodine in patients with differentiated thyroid cancer (DTC) during L-thyroxine treatment.

INTRODUCTION Urinary iodine concentrations were analyzed in the morning urine samples of patients with differentiated thyroid cancer (DTC). MATERIAL AND METHODS The analyzed group included 572 DTC patients who were treated with radioiodine or hospitalized for evaluation of radioiodine treatment effects in 2009 at the Institute of Oncology in Gliwice. Ioduria was analyzed by PAMM (Program Against Micronutrient Malnutrition) method before rhTSH administration. A total of 545 tests were performed during L-thyroxine treatment and 27 after L-thyroxine withdrawal. RESULTS Median L-thyroxine dose was 150 μg/day. Median ioduria was 127.5 μg/L during L-thyroxine therapy and 134 μg/L after the L-thyroxine withdrawal. No distinct relation between ioduria and L-thyroxine dose was observed. Ioduria < 200 μg/L was observed in over 90% of patients and this cut-off was chosen for the reference range. Only 1.2% of patients showed a distinct stable iodine contamination (ioduria ≥ 300 μg/L). CONCLUSIONS Urinary iodine concentrations in differentiated thyroid cancer patients treated with L-thyroxine vary in a wide range and do not show a clear relation with L-thyroxine dose.