A new and sensitive method for quantifying and comparing the biological potency of varius estrogens in man.

The serum level of an estrogen-inducible plasma protein was followed by a radioimmunoassay in groups of women during treatment with various estrogens. After an initial increase, the mean value for the serum concentration was stable. The plateau level after six months of treatment was taken as a parameter of estrogenic potency. Eleven different hormonal preparations were compared and an estrogen index was constructed.