Tibolone has tissue -selective estrogenic effects, with desirable effects in bone , the brain , and the vagina , and lack of undesirable action in the endometrium and breasts .  Its tissue selectivity is the result of metabolism , enzyme modulation (., of estrogen sulfatase and estrogen sulfotransferase ), and receptor modulation that vary in different target tissues, and differs mechanistically from that of selective estrogen receptor modulators (SERMs) such as tamoxifen , which produce their tissue selectivity via means of modulation of the ER.   As such, to distinguish it from SERMs, tibolone has been described as a "selective tissue estrogenic activity regulator" (STEAR),  and also as a "selective estrogen enzyme modulator" (SEEM). 
Risks also increase when combined with other drugs to reduce unwanted side effects .
Decaduro Before & After Pictures Lost 3% body fat ★ ★ ★ ★ ☆ Decreased body fat, increased muscle definition... I’ve seen amazing results in stamina, muscle definition and body fat. Michael A. VIEW REVIEW Lost 20 LB fat & gained muscle ★ ★ ★ ★ ★ I went from 260lbs to 240lbs. My strength definitely increased all around and was able to workout harder and longer. Joey B. VIEW REVIEW Gained 20 LB lean muscle ★ ★ ★ ☆ ☆ Its been a month since I started and I have gained 20 pounds and also went up in strength between 30-60 pounds. James P. VIEW REVIEW Gained 6 LB muscle mass ★ ★ ★ ★ ☆ Ive had a big increase in energy levels and recovery time. I also added about 6lb in muscle mass so far. Jim E. VIEW REVIEW
Stacking Nandrolone Decanoate Stacking or combining other drugs with nandrolone decanoate is a common practice among bodybuilders and athletes in order to enhance benefits or decrease side effects.
Antiestrogens like aromatase inhibitors (., anastrozole ) and selective estrogen receptor modulators (., tamoxifen , raloxifene ) can interfere with and prevent the estrogenic effects of nandrolone decanoate.  5α-Reductase inhibitors like finasteride and dutasteride can prevent the inactivation of nandrolone in so-called "androgenic" tissues like the skin , hair follicles , and prostate gland and may therefore considerably increase its androgenic side effects.  This is opposite to the case of most other AAS, which are either potentiated by 5α-reductase in such tissues or are not substrates of 5α-reductase.  Antiandrogens like cyproterone acetate , spironolactone , and bicalutamide can block both the anabolic and androgenic effects of AAS like nandrolone decanoate.