Thiol-disulfide homeostasis as an oxidative stress marker in patients with Graves' ophthalmopathy.

: To evaluate thiol-disulfide homeostasis (TDH) and its relationship with clinical findings in patients with Graves' ophthalmopathy (GO). : This study included 52 patients with GO and 34 healthy controls. Tests of TDH were conducted using the novel automated spectrophotometric method. Clinical activity score (CAS) and ophthalmopathy index were evaluated and relationships with native thiol, disulfide levels and disulfide/native thiol % ratios were analyzed. : The mean plasma native thiol levels in GO patients were significantly lower than that of normal controls ( = 0.013) . The mean plasma disulfide levels and disulfide/native thiol % ratio were found to be significantly higher in GO patients than in controls ( = 0.041, = 0.022; respectively). The mean native thiol levels of active GO patients ( = 24) were significantly lower than that of patients with inactive GO ( = 28) ( = 0.044). The mean disulfide levels and disulfide/native thiol % ratios of active GO patients were significantly higher than that of patients with inactive GO ( = 0.034, = 0.001; respectively). There was a negative correlation between native thiol and CAS ( = -0.532, = 0.001) and a positive correlation between disulfide/native thiol % ratio and CAS ( = 0.601, < 0.001). : The impairment of TDH indicates the presence of oxidative stress in moderate-to-severe GO, particularly in active GO and smokers.