Objective To explore the thyroid function changes of episodes period and remissions period in children with primary nephrotic syndrome (NS).Methods The urinary protein quantitation and serum albumin,total cholesterol,thyroid hormone level [total triiodothyronine (TT3),total thyroxine (TT4),free triiodothyronine (FT3),free thyroxine (FT4) and thyroid stimulating hormone (TSH)] of episodes period and remissions period in 15 children with primary NS were retrospectively analyzed.Results There were statistical differences in urinary protein quantitation and serum albumin,total cholesterol in children with NS between episodes period and remissions period (P ＜ 0.05).The TT3,TT4,FT3,FT4 in episodes period were significantly lower than those in remissions period [(0.6 ± 0.3) μ g/L vs.(1.3 ± 0.3) μ g/L,(40.0 ± 23.0)μ g/L vs.(68.0 ± 15.0) μ g/L,(1.6 ± 0.3) pmol/L vs.(3.3 ± 0.3) pmol/L,(8.6 ± 2.5) pmol/L vs.(12.2 ± 2.0) pmol/L],TSH was significantly higher than that in remissions period [(5.6 ± 2.1) mU/L vs.(2.5 ± 1.1) mU/L],there were statistical differences (P ＜ 0.05).Conclusions Thyroid function of episodes period in children with primary NS is decreased temporarily,associated with heavy proteinuria leads to thyroid hormone missing from urine.Detecting thyroid function plays an important role in estimating the state and guiding the treatment of primary NS.