Alfatradiol binds to the ERα and ERβ with 58% and 11% of the relative binding affinity of 17β-estradiol.  However, it has 100-fold lower estrogenic activity relative to estradiol,  which may in part be due to differences in the intrinsic activity of the two compounds. [ citation needed ] On the other hand, alfatradiol has been found to bind to and activate the brain -expressed ER-X with a greater potency than estradiol, indicating that it may be the predominant endogenous ligand for the receptor. 
Around fifth part of the injected steroid binds to progestin receptors (due to the absence of a carbon atom in the 19 position), and therefore, such reactions as the suppression of secretion of gonadotropin-releasing hormone, increased production of prolactin, a significant decrease in libido should not be excluded. Weak erection - the most pronounced and severe consequence of abuse of deca nandrolone. Exceeding of the recommended dosage and duration of the course may cause rhinitis, headache, back pain, rash. In general, the side effects of nortestosterone decanoate - rather the exception than the rule.