*Article* **Enhanced Salivary and General Oxidative Stress in Hashimoto's Thyroiditis Women in Euthyreosis**

**Katarzyna Morawska 1, Mateusz Maciejczyk 2,\*, Łukasz Popławski 3, Anna Popławska-Kita 4, Adam Kr ˛etowski <sup>4</sup> and Anna Zalewska 5,\***


Received: 5 June 2020; Accepted: 2 July 2020; Published: 3 July 2020

**Abstract:** Hashimoto's thyroiditis (HT) is one of the most common autoimmune diseases. Although HT is inextricably linked to oxidative stress, there have been no studies assessing salivary redox homeostasis or salivary gland function in patients with HT. This study is the first to compare antioxidant defense and oxidative stress biomarkers in non-stimulated (NWS) and stimulated (SWS) whole saliva and plasma/erythrocytes of HT patients compared to controls. The study included 45 women with HT in the euthyreosis period as well as an age- and gender-matched control group. We showed that NWS secretion was significantly lower in HT patients compared to healthy controls, similar to salivary amylase activity in NWS and SWS. Catalase and peroxidase activities were considerably higher in NWS and SWS of HT patients, while the concentrations of reduced glutathione and uric acid were significantly lower in comparison with healthy subjects. Total antioxidant potential was significantly lower, while total oxidant status and the level of oxidation products of proteins (advanced glycation end products, advanced oxidation protein products) and lipids (malondialdehyde, lipid hydroperoxides) were significantly higher in NWS, SWS and plasma of HT patients. In conclusion, in both salivary glands of women with HT in euthyreosis, the ability to maintain redox homeostasis was hindered. In HT patients we observed oxidative damage to salivary proteins and lipids; thus, some biomarkers of oxidative stress may present a potential diagnostic value.

**Keywords:** Hashimoto's disease; oxidative stress; saliva
