Estrogen blocker work to increase testosterone production by decreasing either aromitization (the conversion of testosterone to estrogen) or by blocking the estrogen receptor. Most supplements on the market work by inhibit the aromatase enzyme responsible for converting testosterone to estrogen. The Hypothalamic Pituitary Testicular Axis (HPTA) senses the levels of androgens (testosterone, DHT, etc.) and estrogens in the body. A decrease in
estrogen levels seeds feedback to the hypothalamus, which sends the signal to increase testosterone production in hopes to aromatize it to estrogen. Since you are taking an aromatase inhibitor, this testosterone is not aromatized to estrogen.
This is very effective in hypogonadal men (i.e. post steroid cycle) in storing testosterone secretion after being supressed and has been shown to work in men with normal testosterone levels as well. How much of an effect something like 6OXO will have an a normal male, I don't know (they did a study, so take that for what it is worth).
Now that PH's are banned, I think test boosters will be the new trend in the supplement market.