Estrone conversion capacity of blood of postmenopausal women with carcinoma of the breast.

During the investigation of the fate of estrone in blood and perfused organs, it was found that@ estrone was converted to a biologically inactive substance (1) , which could no longer be assayed as a 17-ketosteroid (i). Utilization of this latter fact in a study of the conditions under which this con version could occur provided evidence supporting the hypothesis that an enzyme catalyzing the re action is present in blood (@). A number of blood samples from human female donors were found inactive in inducing the con version. In each instance the donor had passed the menopause. Several blood samples from postmeno pausal patients with carcinoma of the breast were found capable of inducing the conversion. The study to be reported was undertaken to determine grossly the extent of the divergence between nor mat postmenopausal women and those with carci noma of the breast.