A Radioimmunological Method for Oestrone

A specific antiserum to oestrone has been used to develop a radioimmunoassay. No chromatographic separation step was included. A small amount of plasma (0.01--0.15 ml) was extracted once with diethyl ehter. The method was used to estimate plasma levels of non-conjugated oestrone in women during uncomplicated late pregnancy. The oestrone plasma concentrations showed a gradual increase from a mean of 4 ng/ml in the 22nd week to 11 ng/ml in the 41st week. Great individual variations were found. No systematic changes of unconjugated oestrone plasma concentrations were noticed during a 24-hour period in late pregnancy. Short term studies revealed that large and rapid fluctuations may appear in the levels of unconjugated oestrone during pregnancy.