Tamoxifen is classed as a specific estrogen receptor modulator or SERM. It acts as an estrogen antagonist in the brain and the breast area meaning it prevents estrogen from exerting its normal effect in those areas. With respect to its action in the brain it inhibits the conversion of testosterone to estrogen which during a cycle can mean that estrogen levels remain low. Although low estrogen is often considered advantageous by bodybuilders it should be noted that estrogen helps both with the accrual of muscle mass and also helps to boost libido on cycle. In fact, when bodybuilders use testosterone enhancing compounds and run Xeno Tamox alongside it, they often lose out on some of the muscle gains and enhanced libido that normally accompanies testosterone elevation.
Tamoxifen dosage used in bodybuilding
Xeno Tamox is typically taken at 40mg per day for the first 2 weeks of a PCT, and then reduced to 20mg daily for the final 2 weeks. Despite this, PCT is not something that is 'one size fits all' and Tamoxifen might not be the right choice for everyone.
By lowering free testosterone, tamoxifen has the potential to hurt our bodybuilding gains. This helps to explain why we never hear of people using tamoxifen on a standalone basis (similar to how a testosterone booster is used) and gaining any muscle mass despite the significant rise in testosterone it is capable of producing. Quite simply, a lot of the testosterone rise is cancelled out by the increase in SHGB. Another negative of tamoxifen's action in the liver is its ability to suppress production of the peptide hormone IGF-1. IGF-1 is broken down from growth hormone and is considered to be more potent than growth hormone itself for the purposes of building muscle tissue. High IGF-1 levels make a big contribution to the process of building a better physique and the ability of tamoxifen to suppress IGF-1 levels is another reason why tamoxifen use tends to be disappointing for the purposes of building muscle mass.