ENDOCRINE REGULATION OF ERYTHROID LINEAGE OF HEMATOPOIESIS IN CHILDREN LIVING UNDER A LOW-DOSE RADIATION EXPOSURE AFTER THE CHORNOBYL NPP ACCIDENT

Abstract

Objective. Elucidation of relationship between the levels of thyroid-stimulating hormone (TSH), free serum thyroxine, serum and urine cortisol and parameters of erythroid lineage of hematopoiesis to estimate the thyroid function in children of prepubertal, pubertal, and postpubertal age permanently residing under a low-dose radiation exposure to determine the premorbid state of thyroid function. Materials and methods. Children aged 3 to 18 years old (n = 203) living in the most intensively radionuclide-contaminated regions of Kyiv, Zhytomyr and Chornihiv oblasts of Ukraine after the Chornobyl NPP accident were enrolled. Complaints of ossalgia, arthralgia, fatigue, bone fractures in the history, bone dysembryogenetic stigmata, hypermobility syndrome degree, and types of somatic diseases were taken into account. Peripheral blood count parameters, biochemical indices of blood serum were studied, namely the levels of total protein, cholesterol, creatinine and alkaline phosphatase activity. Levels of the free thyroxine, pituitary TSH, serum and daily urine cortisol, and doses of radiation exposure were determined. Results. The radiation dose values in children ranged from (0.35 ± 0.09) mSv to (0.54 ± 0.12) mSv. There was no difference between the parameters of erythroid lineage of hematopoiesis depending on radiation dose. At the levels of serum TSH up to 1.0 μIU/ml no correlation was found with cortisol levels; at TSH levels of 1.0–3.0 μIU/ml the correlation coefficient was r = 0.31; at TSH levels higher than 3.0 μIU/ml the correlation coefficient was r = 0.61 probably indicating a compensatory role of adrenal cortex in children at risk of thyroid disease development. In children with joint hypermobility grade II there was a higher incidence of dentofacial anomalies (χ2 = 6.9), deformities of lower extremities (χ2 = 6.9), and dental caries (χ2 = 4.3) (p < 0.05). There was a direct correlation between the serum TSH level (over 3 μIU/ml) and micrognathia (brachygnathia) (r = 0.62) indicating the impact of thyroid disease on dentofacial development. The TSH at a level of upper limit of the reference range values may contribute to a decreased RBC count in peripheral blood, increased average volume and hemoglobin content in erythrocyte being associated with the initial manifestations of thyroid dysfunction. Conclusions. Abnormal endocrine regulation of hematopoiesis affects the connective tissue, stromal microenvironment of bone marrow, and accordingly the erythroid branch of hematopoiesis in children, which may be relevant in the development and course of oncohematological diseases. Key words: children, ChNPP accident, low-dose radiation exposure, erythroid lineage of hematopoiesis, TSH, cortisol, joint hypermobility.