A Radio-ligand Binding Assay System for Estradiol Measurement in Human Plasma

A new, convenient, specific, sensitive, reproducible radio-ligand binding assay system for measurement of estradiol in human plasma has been developed. The procedure compares the ability of standards and unknowns to compete for binding sites on the specific estrogen binding protein of rabbit uterine cytosol. Blank values approached 0. The mean estradiol concentration was 15 pg/ml in post-menopausal women, 24.0 pg/ml in adult men, 65.6 pg/ml during days 1–10 of the menstrual cycle, 124.5 during days 11–20, and 137.2 during days 21–31.