In rodents, estrogens (which are locally aromatized from androgens in the brain) play an important role in psychosexual differentiation, for example, by masculinizing territorial behavior;  the same is not true in humans.  In humans, the masculinizing effects of prenatal androgens on behavior (and other tissues, with the possible exception of effects on bone) appear to act exclusively through the androgen receptor.  Consequently, the utility of rodent models for studying human psychosexual differentiation has been questioned. 
Exemestanes Aromasin is officially classified as a steroidal suicide Aromatase Inhibitor, and carries the ability to inhibit the aromatase enzyme, which is responsible for the production or conversion of testosterone to estrogen. Aromasin has the ability to block aromatization, which in turn inhibits the production of estrogen, and thereby lowers the body’s serum estrogen levels. This will prove useful to breast cancer patients as breast cancer often feeds off the estrogen hormone. It will also prove useful to the anabolic steroid user.
Compounds are tested for their estrogen receptor activity in a binding assay and in a transactivation assay.
Determination of competitive binding to cytoplasmic human estrogen receptor from
cells is used to estimate the relative affinity (potency ratio) of a test compound for estrogen receptors present in the cytosol of recombinant Chinese hamster ovary (CHO) cells, stably transfected with the human estrogen receptor, as compared with estradiol (E2).
Cytosol prepared from recombinant CHO cells, stably transfected with the human estrogen receptor.
The cell line has been made within the Department of Biotechnology and Biochemistry (BBC) (. Organon) and is known under the name CHO-ER (2B1). Reference compounds are ethinylestradiol and estriol.
The antiestrogenic activity of compounds is determined in an in vitro bioassay with recombinant Chinese hamster ovary (CHO) cells stably co-transfected with the human estrogen receptor a(hERa) or (3 receptor (hER(3), the rat oxytocin promoter (RO) and the luciferase reporter gene (LUC). The antiestrogenic activity (potency ratio) of a test compound to inhibit the transactivation of the enzyme luciferase mediated via the estrogen receptor by the estrogen Org 2317 (estradiol, 1, 3, 5(10)-estratriene-3, 17B-diol) is compared with the standard Org 34790 (ICI ; (7(x,17B)-N-butyl-3,17-dihydroxy-N-methylestra-1,3,5 (1 0)-triene-7-undecanamide).
Test medium: Intact recombinant CHO cells stably co-transfected with the human estrogen receptor, the rat oxytocin promoter and the luciferase reporter gene. The cell line has been produced within the Department of Biotechnology and Biochemistry (BBC) (.
Organon) and is known under the name CHO-ERRO 2B 1-1 E9.
The results are presented in the Table below.