Estrogen receptor assay of mammary carcinomas. Effects of testosterone-estradiol-binding globulin (TeBG) and serum estradiol-17 beta.

To test the hypothesis that the serum sex steroid-binding protein, TeBG, might contaminate mammary carcinoma cytosols sufficiently to interfere with assay for estrogen receptor (ER), studies of tritiated estradiol-17 beta (3H-E2) binding were done following saturation with steroid hormones or after heat treatment of cytosol. Cytosols with appreciable 3H-E2 binding consistently showed a high degree of saturability with nonradioactive E2 and diethylstilbestrol (DES), and much less saturability with 5 alpha-dihydrotestosterone (DHT). Furthermore, they manifested heat-lability of 3H-E2 binding. These characteristics indicated that little, if any, TeBG was being detected in most cytosols, and that the amounts of TeBG present were not sufficient to interfere with the ER assay. Study of the relationship between serum E2 concentration at time of removal of the carcinoma and results of ER assay confirmed the need to interpret negative ER assays obtained for premenopausal women cautiously when serum E2 levels exceed approximately 300 pg/ml.