Anderson JLC, et al. - This study is performed to compare the connections of thyroid stimulating hormone (TSH), free thyroxine (FT4) and free triiodothyronine (FT3) with various measures of kidney function in euthyroid subjects. In euthyroid subjects renal function is related to thyroid function status, especially by serum FT3, irrespective of the eGFR equation applied. In the euthyroid state, cystatin C-based eGFR equations are appropriate to evaluate the relationship of renal function with variation in thyroid function status.