Original article Determination of oxidative stress in thyroid tissue and plasma of patients with Graves' disease Evin Ademoğlu a , Neşe Özbey b , Yeşim Erbil c, ⁎ , Sevda Tanrikulu a , Umut Barbaros a , Burcu Tulumoğlu Yanik c , Alp Bozbora a , Selçuk Özarmağan a a Istanbul University, Istanbul Medical Faculty, Department of Biochemistry, Turkey b Istanbul University, Istanbul Medical Faculty, Department of Endocrinology, Turkey c Istanbul University, Istanbul Medical Faculty, Department of General Surgery, 34340, CAPA, Istanbul, Turkey Received 21 December 2005; received in revised form 8 April 2006; accepted 27 April 2006 Abstract Background: The aim of our study was to evaluate the oxidant/antioxidant status of thyroid tissue in Graves' disease (GD) patients and to compare the results of GD thyroid tissue with plasma of patients and healthy controls. Methods: We studied 25 consecutive patients with GD hyperthyroidism who underwent surgical treatment. The patients were divided into groups according to the duration of antithyroid drug treatment, the type of antithyroid drugs used, the presence of ophthalmopathy, and recurrence after a complete course of antithyroid drugs. Thiobarbituric acid-reacting substances (TBARS), glutathione peroxidase (GPx) activity, superoxide dismutase (SOD) activity, and total thiol (t-SH) content of tissue and plasma samples were determined. Results: TBARS concentrations were found to be significantly increased in GD patients' plasma compared with controls' plasma (0.1 ± 0.02 nmol/mg protein vs. 0.062 ± 0.01 nmol/mg protein). Significantly decreased t-SH concentrations were measured in GD patients' plasma compared with controls (8.26 ± 1.9 nmol/mg protein vs. 13.03 ± 3.3 nmol/mg protein). Tissue TBARS, t-SH, GPx, and SOD measurements in GD patients indicated significantly increased concentrations compared with the plasma levels of patients. Patients with shorter treatment duration before the operation had significantly increased plasma and tissue TBARS and decreased plasma and tissue t-SH concentrations. Patients on propylthiouracil treatment had significantly lower plasma and tissue concentrations of TBARS than patients on methimazole. Patients with recurrence had significantly higher plasma and tissue TBARS and lower plasma and tissue t-SH concentrations than patients treated for the first time. Conclusions: In euthyroid GD patients on antithyroid drugs, increased oxidative stress and a compensatory increase in the antioxidant defense system are more prominent in thyroid tissue than in plasma. Patients who relapsed had markers indicating increased oxidative stress. Thus, ongoing autoimmunity may contribute to increased oxidative stress in GD patients, even in the euthyroid state. © 2006 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved. Keywords: Graves' disease; Oxidant/antioxidant properties; Antithyroid drugs 1. Introduction Reactive oxygen species (ROS) produced during the course of a lifetime can damage proteins, nucleic acid, and lipids [1,2]. Oxidative damage from polyunsaturated fatty acids leads to the formation of thiobarbituric acid-reacting substances (TBARS). ROS generation is controlled by anti- oxidant enzyme activities [superoxide dismutase (SOD), glutathione peroxidase (GPx)] and non-enzymatic antiox- idants such as glutathione (GSH) and total thiol content (t- SH) of tissues and plasma [3,4]. Previous studies have indicated an imbalance between oxidant/antioxidant status and enhanced oxidative stress in hyperthyroidism [5–8]. In these studies, plasma and/or eryth- rocyte markers of oxidant/antioxidant status were examined. As far as we know, the oxidative status of thyroid tissue in Graves' disease (GD) has not been reported previously. European Journal of Internal Medicine 17 (2006) 545 – 550 www.elsevier.com/locate/ejim ⁎ Corresponding author. Tel.: +90 212 5331784; fax: +90 212 6319771. E-mail address: yerbil2003@yahoo.com (Y. Erbil). 0953-6205/$ - see front matter © 2006 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.ejim.2006.04.013