The renal clearance of oestriol in late human pregnancy

The renal clearance of unconjugated oestriol, oestriol glucosiduronate and oestriol sulphate by the kidney in late human pregnancy has been compared with simultaneous measurements of inulin clearance. The results for the fractions not bound to protein indicate that after glomerular filtration, unconjugated oestriol is completely reabsorbed, oestriol glucosiduronate is both filtered and excreted actively by the tubules, and that oestriol sulphate is filtered but not excreted or absorbed by the tubules; the administration of probenecid confirms these observations on tubular handling. The possibility of using endogenous oestril sulphate as a means of measuring the glomerular filtration rate in pregnancy is suggested.