Iodine metabolism in hyperthyroidism
Jolanta Kijek1, Jerzy S Tarach2, Maria Kurowska2 & Beata Chrapko1
Introduction: Iodine is critical for thyroid morphology and function. On the one hand, iodine is a factor leading and permitting to origin of disturbances of thyroid follicular cells function, on the other hand, its therapeutic agent.
Aim: The aim of the study was to evaluate iodine metabolism in different forms of hyperthyroidism and to analyze relationship between metabolism and thyroid size and function.
Material and methods: The study group consisted of 300 patients (236F and 37M) aged 2080 years (mean 50.5). About 150 patients with Graves disease (GD) and 150 with toxic nodular goiter (TNG). Thyroid technetium-99m scans was performed and serum levels of fT3, fT4 (FIA method), TSH (IFMA method) and TSI (radioreceptor method) were determined. Iodine uptake (RIU) was measured after 24 and 48 h, then effective half-life (EHL-RIU) was determined. In 200 patients PBI was measured after 24 and 48 h, then effective half-life (EHL-PBI) was estimated.
Results: RIU and PBI values are higher and effective half-life is shorter in GD than in THG. In 300 patients, correlation was found between RIU and age, fT3, fT4, TSI, thyroid mass. PBI was related to TSH, fT3, fT4, TSI, thyroid mass. EHL-RIU was related to TSH, fT3, fT4, thyroid mass. EHL-PBI was related to TSH, fT3, fT4 and TSI. In GD, EHL-RIU was related to fT3, fT4 and TSI, PBI and EHL-PBI were related to TSI. In TNG correlation was found between RIU, effective half-live, PBI and fT3, fT4, TSH, thyroid mass.
Conclusions: In GD, RIU is higher and iodine turnover is faster that in TNG. In TNG relationship between RIU and thyroid mass, function can be found. In GD, iodine kinetics are related to thyroid function, immunization level; in TNG to thyroid mass and function. Its necessary to determine form of hyperthyroidism while analyzing results.