Antioxidant Defense in Overt and Subclinical Hypothyroidism

Abstract

Oxidative stress as a result of disequilibrium between free radical generation and antioxidant status has been implicated in several pathologies including thyroid diseases. Studies on antioxidant status in overt (OHT) and subclinical hypothyroidism (SHT) are controversial and limited. The aim of this study was to determine the effect of OHT and SHT on antioxidant status. Thirty-six patients with OHT, 36 patients with SHT, and 39 healthy euthyroid subjects as the control group were included in the study. Plasma levels of malondialdehyde (MDA), reduced glutathione (GSH) and total antioxidant capacity (TAC) as ferric reducing ability of plasma (FRAP), and erythrocyte antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GPx), SOD/GPx ratios, catalase (CAT), and glutathione reductase (GR) were analyzed in all groups. MDA and GPx values were elevated, while GSH, FRAP, SOD, and SOD/GPx ratio were decreased in both patient groups compared with controls. No change in activities of CAT and GR were observed in both the patient groups. Significant differences were observed between OHT and SHT groups with high MDA, GPX and low GSH, FRAP, SOD, and SOD/GPx ratio in OHT group. Thus, hypothyroid patients have a deficient antioxidant defense in the form of decreased activity of SOD, decreased levels of FRAP and GSH along with an increase in GPx activity. The severity of the disease appears to decide the degree of deficiency and our findings also point to this, in the form of decrease in SOD, FRAP, and GSH observed being more in OHT than in SHT patients. Hormonal changes and increased lipid peroxidation, which also vary with severity of disease, appear to contribute to the antioxidant deficiency.

Comparison of therapeutic effects of L-Thyroxin, apelin and a combination of both on antioxidant enzymes in the heart of PTU-induced hypothyroid rats

“…There are some data that show in patients with hypothyroidism, oxidative stress, is increased (Lampka et al 2006;Sarandol et al 2005), decreased (Venditti et al 1997) or remain unchanged (Coria et al 2009). In agreement with the results of the current study, Reddy, et al demonstrated that the serum level of MDA and GPx activity increase in hypothyroid and subclinical hypothyroid patients (Reddy et al 2013). Another study showed that lipid peroxidation increase and an antioxidant level decrease in blood of hypothyroid patients (Dumitriu et al 1988).…”

Subclinical hypothyroidism and vascular risk: Αn update

“…96 Although there is no evidence that antioxidants reduce vascular risk, it is of interest that severity of hypothyroidism appears to contribute to the antioxidant deficiency and oxidant stress. 97,98 SCH is related to non-alcoholic fatty liver disease (NAFLD) in a dose-dependent manner independently of metabolic risk factors. 99 Moreover, NAFLD and abnormal liver tests are associated with an increased risk of vascular events.…”

Associations of FPG, A1C and disease duration with protein markers of oxidative damage and antioxidative defense in type 2 diabetes and diabetic retinopathy

“…OS has been implicated in the pathogenesis of over 100 human diseases, including endocrine disorders. 1,2 Diabetes is the most prevalent, leading endocrine disorder worldwide. Type 2 diabetes mellitus (DM) has been described as a global epidemic with the estimates of 171 million diabetics in 2000, expected an increase to 366-440 million by 2030.…”