[Involvement of essential trace elements in the pathogenesis of thyroid diseases: diagnostic markers and analytical methods for determination].

Abstract

Aim: To study the role of iodine, selenium and zinc in the pathogenesis of iodine deficiency and autoimmune thyroid diseases and scientifically substantiate the choice of security biomarkers and analytical methods for determination.

Materials and methods: Serum iodine (I), selenium (Se), and zinc (Zn) concentrations were measured using inductively coupled plasma ionization tandem mass spectrometry (Agilent 8900 ICP-MS Triple Quad); by chemiluminescent immunoassay on an automatic analyzer Architect i2000 - TSH and AT-TPO in blood serum; by enzyme immunoassay - ZnT8A; biochemical method - ALP, SOD1 in 1150 people aged from 18 to 65 years (the average age of the subjects was 40±5 years). Ultrasound of the thyroid gland was performed in the supine position using a portable ultrasound machine LOGIQe with a multifrequency linear sensor 10-15 MHz; during the study, the volume of the thyroid gland, the presence of nodules and their characteristics according to the TIRADS classification, the structure of the thyroid gland and its echogenicity were assessed.

Results: In our study, the median serum iodine concentration was 60.68 μg/L (n=1150), with no significant difference between sexes. In 2%, the level of iodine in the blood serum was less than 30 mcg/l. Among the samples obtained (n=57), 19% were found to have a reduced iodine content in the lipophilic fraction - less than 10% of the total. In these samples, additional studies were performed on TSH, total and free T3 and T4 fractions. As a result, all indicators fell within the normal range, which indicates that there was no effect on thyroid function from a decrease in iodine content in the lipophilic fraction. In a comparative analysis of our previously obtained results of determining iodine in urine using the cerium-arsenite method and the inductively coupled plasma mass spectrometry method, it was found that both methods are generally comparable. The median selenium concentration was 83.38 µg/l, which corresponds to the reference values. The proportion of individuals with serum selenium levels less than 40 μg/L was 2.2%. A comparative analysis of groups of patients with serum selenium concentrations of less than 100 µg/l and more than 100 µg/l was carried out; in the group with low-normal selenium levels, the incidence of autoimmune thyroid pathology is 5% higher than in the comparison group. 60.3% of the adult population had zinc levels less than 1000 μg/L. The median serum zinc concentration was 632.9 μg/L. In regions with zinc deficiency, the incidence of autoimmune diseases (AI) of the thyroid gland and nodular / multinodular goiter is on average 10% higher than in regions with optimal zinc supply. There was no relationship between the content of zinc in the blood serum and antibodies to the zinc transporter (ZnT8A), alkaline phosphatase (ALP) and superoxide dismutase (SOD1), including in comparison of the data obtained in carriers of AT-TPO and in the comparison group (among carriers of AT-TPO: the median concentration of zinc was 644.4 μg/l, SOD1 - 117.2 ng/ml, ALP - 70.3 U/l, antibodies to ZnT8A - 249.8; in the comparison group - median zinc concentration - 744.6 μg/l, SOD1 - 102.4 ng/ml, ALP - 66.1 U/l, antibodies to ZnT8A - 242).Thus, based on the data obtained, the relationship between thyroid pathology and micronutrient deficiencies was confirmed. No convincing evidence has been obtained on the study of additional diagnostic markers of Zn deficiency, which casts doubt on the advisability of their determination in routine practice. The ICP-MS method made it possible to propose its own reference values for I, Se, Zn and is comparable to the cerium-arsenite method in sensitivity and specificity when studying I in urine. However, due to technical features and limitations in sample size, the study population requires further improvement.