Association Between Thyroid Hormones, Lipids and Oxidative Stress Markers in Subclinical Hypothyroidism / Povezanost Izme\U Tireoidnih Hormona, Lipida I Markera Oksidativnog Stresa U SubkliniĉKoj Hipotireozi

Abstract

SummaryBackgroundOxidative stress plays a role in the pathogenesis of many chronic diseases. It is recognized in overt hypothyroidism while its existence in subclinical hypothyroidism (SCH) is not well established. The aim of this study was to determine whether there was increased oxidation of lipids and proteins in SCH, and examine their association with lipids and thyroid hormones.MethodsMale adults (35–59 years) with SCH (n=467) and euthyroid controls (n=190) were studied. Anthropometric measurements, plasma lipids, thyroid stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), total antioxidant capacity (T-AOC), lipid peroxidation products, malondialdehyde (MDA), advanced oxidation protein products (AOPP) and dityrosine concentrations were measured.ResultsPlasma concentrations of MDA were significantly higher (p<0.05) in SCH (8.11±1.39 nmol/mL) compared with euthyroid controls (7.34±1.31 nmol/mL) while AOPP, dityrosine and T-AOC levels were not different. MDA was not associated with TSH (β=−0.019, P=0.759), FT4 (β=−0.062, P=0.323) and FT3 (β=−0.018, P=0.780) in SCH while levels increased with elevated total cholesterol (β=0.229, P=0.001), LDL (β=0.203, P=0.009) and triglycerides (β=0.159, P=0.036) after adjustment for age and body mass index. T-AOC reduced (β=−0.327, P=0.030) with increased MDA in euthyroid controls and not in SCH (β=−0.068, P=0.349), while levels increased with elevated triglycerides in both groups.ConclusionsOxidative stress was increased in subclinical hypothyroidism as evidenced by the elevated lipid peroxidation product, malondialdehyde, while protein oxidation was absent. Thus, reduction of oxidative stress may be beneficial in patients with subclinical hypothyroidism.

Direct Estimation of Reference Intervals for Thyroid Parameters in the Republic of Srpska

“…Inter-individual variations are particularly high for the serum concentration of Tg, because there are differences in the weight of the thyroid gland in different individuals, the status of TSH, and there are also conditions associated with thyroid injury (thyroiditis) – all of these conditions are affected by the serum concentration of Tg ( 31 ). Although there is statistically significant difference in the values of TSH and fT3 between different age groups ( Table II ), we cannot say that our study is consistent with the results of other studies ( 35 – 37 ) in which the levels of TSH and free T3 gradually declined in older age. When we analyzed the TSH and T4 levels in the male and female population, we found no statistically significant difference between these two groups, but for the fT4, T3 and fT3 values we found significant difference ( Table III ).…”

Oxidative DNA damage and subclinical hypothyroidism in children with obesity

“…Oxidative stress is strongly linked to inflammation with several reports demonstrated significant increase in oxidation stress in children with obesity that plays a key role in the development of obesity complications [24]. Several studies reported higher oxidative stress in subjects with subclinical hypothyroidism [25]. However, our study showed no significant difference in oxidative DNA damage between obese and normal weight children with no significant association between 8-hydroxydeoxyguanosine and subclinical hypothyroidism.…”

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

“…However, persistent hyperlipidemia can lead to antioxidant system overload and, subsequently, to a decrease in the level of antioxidant defense. As a consequence, with progressive hyperlipidemia, oxidative stress increases, which is observed in subclinical hypothyroidism (Yang et al, 2008;Cheserek et al, 2015). The effect is confirmed by a significant correlation between MDA and LDL-cholesterol levels, total cholesterol and triglycerides levels.…”

“…Perhaps the main role in the formation of malonic dialdehyde level in the experimental group was performed by specific lipid profile. Some authors believe that oxidative stress and MDA growth in hypothyroidism (both expressed and subclinical) are caused not by direct changes in thyroid status, but by changes in the lipid profile caused by thyroid dysfunction (Santi et al, 2012;Anjaneyulu et al, 2015;Cheserek et al, 2015). Prolonged availability of oxidative substrates (mainly low density lipoprotein cholesterol, LDL-C) in plasma increases their susceptibility to oxidative modification (Napoli et al, 1995).…”