Background: The interactions between kidney and thyroid functions have been known for many years; oxidative damage has been proposed as one of the possible mechanism involved in the nephrotic syndrome (NS). This study was done to find out the thyroid function of nephrotic children during nephrosis and to compare any significant changes of thyroid function status during nephrosis and remission in relation to oxidative stress markers. Patients and Methods:The study included 60 patients with steroid responsive NS (SRNS) and 30 children with matched age and sex as control. Cases were divided into three groups as follow, Group A: Include 35 patients with SRNS in relapse. Group B: Include 25 patients with SRNS in remission for periods ranging from 3 to 9 months, and not receiving steroid therapy. Group C: Include 30 children with matched age and sex as control. Methods: A thorough history and examinations, total serum thyroxine and triiodothyronine (TT4 and TT3) as well as serum free T4 (FT4), thyroid-stimulating hormone (TSH), and assessment of malondialdehyde (MDA) and total antioxidant capacity (TAC) levels as an oxidative stress markers were measured in all studied groups. Results:Serum TSH was significantly higher in patients with SRNS in relapse in comparison with patients with SRNS in remission and with control group (P 0.001 in both), we found a significant decrease in TT4 and FT4 and TT3 and FT3 (FT3) concentrations in patients with SRNS in relapse in comparison with both cases with SRNS in remission and control group (P 0.001 in both). MDA levels were significantly elevated, while TAC level was significantly decreased in patients with SRNS in relapse in comparison with patients with SRNS in remission and with control group (P 0.001 in both). There was a positive correlation between serum TSH and plasma MDA and a negative correlation with FT4. Conclusions:The development of hypothyroidism in children with SRNS is associated with alteration in oxidant and antioxidant status. The biochemical hypothyroid state in relapse phase is temporary and improves with remission.