Interdependence of oxidative/antioxidant system indicators and thyroid status under conditions of prolonged exposure to small doses of radiation

Abstract

We have studied the interdependence of the intensity of oxidative processes/antioxidant level and the thyroid status parameters in a group of students aged 18–24 who lived for a long time in the territory of enhanced radioecological control (density of soil contamination by isotopes (137Cs 3.7 ∙ 104 – 18.5 ∙ 104 Bq/m2). We examined 50 people from relatively environmentally friendly areas (control group) and 50 people from IV radiation zone (experimental group). In the experimental group, there were no individuals with clinical manifestations of thyroid pathology. However, subgroups with signs of hyperthyroidism and hypothyroidism were identified. We evaluated the level of cortisol, thyrotrophic hormone (TSH), triiodothyronine (T3), thyroxine (T4), malonic dialdehyde (MDA), ceruloplasmin (CP), transferrin (Tf), sulfhydryl groups (SH); we calculated the oxidative stress index (OSI). The research was conducted one month before the examination time and also during the exams as a factor in increased emotional stress. A lowered CP level was found in the subgroup with signs of hypothyroidism; SH groups – in all subgroups, separated by thyroid status. The oxidative stress index was higher in all students examined of the experimental group, compared with the control. The growth of MDA level is marked in the experimental group – it is the most strongly pronounced in conditions of additional emotional load in people with signs of hyperthyroidism and hypothyroidism. CP level significantly decreased in the subgroup of hyperthyroidism on the background of T3 decrease. OSI increased in all students examined from the experimental group. In the subgroup of hypothyroidism it became significantly higher than in the subgroup of euthyroidism. A positive correlation between the levels of CP and T3 was found. The highest values of the correlation coefficients were noted for subgroups with signs of hyperthyroidism and hypothyroidism, with the coefficient significance increasing under conditions of emotional stress. The index of oxidative stress in the experimental group positively correlated with the level of TSH – in terms of emotional stress, the statistical significance of the coefficients disappeared. In the subgroups divided by thyroid status, variability of interactions between OSI and T3 was observed but it was not statistically significant. It was found that the participation of thyroid status in supporting redox homeostasis in people aged 18–24 who suffered from chronic small-doze radiation exposure was realized mainly by the influence on the antioxidant system. The ability of thyroid hormones to maintain a proper antioxidant state was suppressed in this group. The unbalanced relationship between thyroid hormones and oxidative stress indicators is strongly manifested under conditions of additional emotional stress.

Parameters of lipid and oxidative-antioxidant status in persons aged 18-23 from radiation-contaminated areas under conditions of moderate physical activity

“…However, cortisol rate did not reach such high values as in the period of intensified psycho-emotional load caused by the examination session. This effect, when cortisol level also increased in the control group, was observed in our previous studies [24,25]. Thus, we can distinguish the lack of the evident stress effect of physical activity.…”

“…In our previous studies, we have found an increase in oxidative stress in people who have lived for a long time in radiation-contaminated areas. Also the signs of lipid status disorders were discovered [23][24][25]. However, in the same cohort, dosed physical exercise during physical training classes led to short-term changes in the immune system within the homeostatic norm.…”

“…Biomaterial collection techniques, used in the study reagents and methods for assessing the level of cortisol, lipid and oxidative-antioxidant status are described in detail in previous publications [23][24][25]. To assess the intensity of oxidative processes used the method developed by Korol and Myhal [27].…”

Manifestations of allostatic load in residents of radiation contaminated areas aged 18–24 years

“…We have shown that the examined students from the experimental group experienced an intensification of oxidation processes (in particular, at the level of the oxidative stress index), especially pronounced under conditions of additional emotional load. The redox homeostasis imbalance has been associated with the signs of thyroid dysfunction (especially with a state of hypothyroidism) and proatherogenic changes in the lipid profile (Sokolenko & Sokolenko, 2019) and it is reflected in immune system indicators (Sokolenko et al, 2018). However, neither the level of malondialdehyde nor the level of analyzed antioxidant factors went beyond the homeostatic norm, so they were not indicated as significant bioindicators of the allostatic load of the examined students, the calculation of the relative risk of maladaptive processes was not performed for them.…”

“…Biomaterial sampling techniques, reagents and research methods used have been described in detail in previous publications: evaluation of erythrocyte (AB0, Rhesus) and serum (haptoglobin Hp system) genetic blood systems (Sokolenko, 2016b), lipid metabolism (Sokolenko & Sokolenko, 2017b), the immune system and oxidative-antioxidant status (Sokolenko et al, 2018), cortisol and thyroid status (Sokolenko & Sokolenko, 2019). The diagnosis of vegetative-vascular dystonia (VVD) syndrome was set by the doctors of the sanatorium "Edem" at the university.…”