Serum oestradiol-17 beta in normal women.

Serum concentrations of oestradiol-17β were measured by radio-immunoassay during 40 menstrual cycles from 38 normal premenopausal women. Repeated samples were studied from 25 normal postmenopausal women. The method was highly specific and extremely sensitive. In premenopausal women the pattern of serum oestradiol-17β was remarkably constant but the concentrations varied with age. Women in the fourth decade of life had significantly higher concentrations of oestradiol-17β than either younger or older women. In postmenopausal women the concentration of oestradiol-17β was consistently very low.