Differential diagnosis of thyroid diseases by the x-ray fluorescent method

Intrathyroid stable iodine (ISI) was measured in 249 women aged 36 to 55 living in Moscow. 179 of these suffered from thyroid tumors and autoimmune thyroiditis and 70 without history of thyroid diseases with normal thyroid status confirmed by clinical laboratory data and ISI values of at least 200 pg/g, considered as the critical, were controls. ISI concentrations were measured using a Russian commercial sample for noninvasive x-ray fluorescent analysis. Using the same device, ISI was measured in thyroid samples with cancer and benign tumors, embedded in paraffin blocks, sent from the USA (n - 47) and Russia (n = 126); in addition, these samples were examined histologically. ISI concentrations were lower in cancer, thyroid adenomas, and autoimmune thyroiditis than in control. An ISI concentration lower than 200 pg/g indicates autoimmune thyroiditis with a probability of 96%. Use of L- thyroxin test increases the probability of the disease recognition to 98%.