Analysis of free estrone and 17β-estradiol in plasma by tritiated sodium borohydride reduction

Abstract A method for the determination of free estrone and 17β-estradiol in the plasma of nonpregnant and pregnant women is described. The method is a double isotpe derivative procedure in which tritium-labeled sodium borohydride is utilized as the labeling agent, and experiments designed to demonstrate its validity are presented. The results obtained when the method was applied to blood samples from two normal women throughout a normal menstrual cycle are given. The data show that there is a pronounced midcycle peak in the concentration of 17β-estradiol in these subjects.