Possible association of primary open-angle glaucoma with thyroid dysfunction and oxidative stress

Abstract

Background Primary open-angle glaucoma (POAG) is a leading cause of blindness worldwide. Thyroid dysfunction and oxidative stress can be associated with POAG. Purpose The aim of this study was to determine whether thyroid dysfunction (hypothyroidism or hyperthyroidism) is associated with glaucoma in Egyptian patients and to evaluate the level of oxidative stress (OS) markers in the serum of POAG patients. It also aimed to investigate the relationship between the OS markers and thyroid hormones in those patients. Patients and methods The study included 60 patients with POAG who were compared with 20 normal controls. Serum samples from the POAG patients and controls were examined for thyroid hormones [triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH)] using the ELISA technique. The OS markers [hydrogen peroxide (H2O2), nitric oxide (NO), malondialdehyde (MDA), and reduced glutathione (GSH)] were also determined using colorimetric methods. Results There were no significant differences in the levels of T4 and TSH in the patients (3.14±2.25 ng/dl and 2.43±1.37 u/l, respectively) compared with the controls (3.35±1.88 ng/dl and 1.76±0.99 u/l, respectively) (P=0.245 and 0.064, respectively). However, there was a significant decrease in the T3 level in the POAG patients (2.88±0.54 pg/ml) compared with the controls (3.35±0.6 pg/ml) (P=0.029). In addition, there was a significant increase in the levels of H2O2 (2.83±1.66 mM/l), NO (54.64±29.21 umol/l), and MDA (164.12±96.5 nmol/ml) in the patients compared with the controls (0.83±0.55 mMol/l, 22.49±6.37 umol/l, and 44.36±12.59 nmol/ml, respectively) (P<0.001). There was also a significant decrease in the level of GSH in patients (54.32±32.1 mg/dl) compared with controls (103.99±45.52 mg/dl), (P<0.001). A significant negative correlation was detected between TSH and T4 (r=−0.41, P= 0.001), TSH and MDA (r=−0.27, P=0.04), T3 and H2O2 (r=−0.05, P=0.05), and T4 and NO (r=−0.35, P=0.01). Conclusion There was no association between POAG and thyroid dysfunction. However, the POAG patients are susceptible to OS and damage, as they had elevated serum levels of H2O2, NO, and MDA and reduced levels of GSH. Since the thyroid hormone level was associated with the OS markers, antioxidant therapy may be beneficial and may help to regulate the intraocular pressure and protect the trabecular meshwork cells from OS in those patients.