Currently, the theory of oxidative stress (OS) is considered to be one of the most important, which explains the appearance and progression of many diseases, especially the cardiovascular system (CVD), diabetes mellitus (DM), as well as the relationship between the OS and aging processes. The growth of an OS during aging is a consequence of a decrease in the AD efficiency. Endocrine disorders significantly affect the OS and AD. Older people are thought to be more sensitive to thyroid hormones than young people. The relationship between the level of thyroid hormones and AD is not fully understood. Therefore, there remains the relevance of revealing informative and accessible criteria for assessing the adequacy of hypothyroidism therapy with regard to the level of OS activity and the AD state. The purpose of the study was to evaluate the influence of the thyroid gland functional state on the level of antioxidant defense in different age patients with comorbid course of hypertension (HT), type 2 diabetes mellitus (DM2T), and subclinical hypothyroidism (SH). Material and methods. 127 patients aged from 45 to 75 with AH of the II stage and compensated DM2T were examined. SH was diagnosed in 48 patients. All patients were divided into 4 groups: group 1 (n = 33) included patients with HT and DM2T aged 45-59, group 2 (n=35) enumerated patients with HT and DM2T from 60 to 75 years old, group 3 (n = 30) comprised patients with HT, DM2T and SH from 45 to 59 years old, and group 4 (n=29) had patients with HT, DM2T and SH aged 60-75. The control group consisted of 20 healthy volunteers representing gender and age. AD system was evaluated by the activity of glutathione peroxidase (GPO), the level of sulfhydryl groups (SH-groups). The level of malondialdehyde (MDA) was used as a marker of oxidative stress, 8-hydroxy-2-deoxyguanosine (8-OH-dG) was assessed as a marker of oxidative DNA damage. Results and discussion. As a result of evaluating the patients with HT and various combinations of endocrinopathies like DM2T and SH, feature of the OS and changes in the AD system activity were dependent on both the thyroid functional state and the patient's age. MDA levels were significantly higher (p<0.05) in all groups, compared to control, but the highest was in patients with hypertension, DM2T and SH. The MDA levels had insignificant age-related changes in the groups of patients with HT and DM2T (p> 0.05) and was significantly higher when combined with DM2T and SH in patients aged 45-59 (p<0,05) than in patients with a similar combination of pathologies at the age of 60-75 (MDA: 4.07 ± 0.22 μmol/l, 6.45 ± 0, 33 μmol/l, 6.57 ± 0.59 μmol/l, 7.19 ± 0.37 μmol/l, 6.81 ± 0.36 μmol/l, respectively in control, 1, 2, 3 and 4 groups). We revealed progressive and significant (p<0.05) reduction of the GPO levels in patients from the 1st to the 4th groups compared with the control group. Levels of GPO in groups of HT with DM2T and SH were lower (p<0.05) than in patients who combined HT only with DM2T. Age-related changes also contributed to decrease in GPO levels, although these changes were not significant (p>0.05). In control, 1, 2, 3 and 4 groups, GPO (µkat/gHb) had the following values: 6.77 ± 0,52, µkat/gHb, 5.59 ± 0.41 µkat/gHb, 5.10 ± 0.27 µkat/gHb, 4.98 ± 0.18 µkat/gHb, 4.78 ± 0.12 µkat/gHb, respectively. The obtained data showed a progressive decrease of the SH-groups levels in all groups of patients depended on the comorbidity of diseases and patient’s age. At the same time, changes related to the thyroid gland functional state were significant (p<0.05). The changes associated with age were not significant (p> 0.05), but characterized by a steady tendency to decline (SH-groups (μmol/l): 712.26 ± 13.08 μmol/l, 595.82 ± 12.14 μmol/l, 554.12 ± 11.34 μmol/l, 580.21 ± 15.03 μmol/l, 551.54 ± 10.67 μmol/l in control, 1, 2, 3 and 4 groups, respectively). The values of 8-OH-dG are more pronounced in age groups in spite of comorbidity. Conclusions. Thus, the study showed that the presence of subclinical hypothyroidism in patients with comorbid pathology was accompanied by an increase in oxidative stress manifestations, regardless of age, on the background of decreased antioxidant defense activity, more pronounced in the older age groups.
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