This study evaluated oxidative stress, serum IgM and IgG, and nuclear factor (NF)-kappaB signaling in lymphocytes of hyperthyroidism patients. GSH content in lymphocytes was significantly lower and serum malondialdehyde, IgM and IgG levels were significantly higher in hyperthyroidism as compared to controls. In lymphocytes, the NF-kappaB signaling pathway was studied by western blot analysis of p65 and p-IkappaBalpha. Density of p-IkappaBalpha and p65 (in nuclear fraction) was significantly higher in hyperthyroidism as compared to controls. The density of p-IkappaBalpha and p65 had significant positive correlation with serum malondialdehyde level and negative correlation with lymphocyte GSH level in hyperthyroid cases. The serum IgG and IgM levels were correlated significantly with density of p-IkappaBalpha and p65. As immunoglobulin production is regulated by the NF-kappaB pathway, we conclude that the oxidative stress-induced activation of the NF-kappaB pathway might play a role in the rise of serum immunoglobulin level in hyperthyroidism.