Updated: Jul 6, 2019
Despite the misunderstanding surrounding the term "AI", Tamoxifen (Nolvadex) is not an aromatase inhibitor. Tamoxifen is a selective estrogen receptor modulator or SERM. There is a significant difference between inhibition of aromatase and receptor interaction. Aromatase inhibition means to cease or slow the conversion and metabolization of testosterone into Estrogen (E2,4,16 etc)
Anastrozole is an aromatase inhibitor. Typically, medical treatment for breast cancer leverages both Tamoxifen and Anastrozole in order to decrease both estrogen production and binding to the breast tissue. Anastrozole actually suppresses conversion to estrogen by limiting the aromatase enzyme and preventing conversion, hence aromatase inhibitor. This means that Anastrozole actually lowers the e2,e4,e16 levels in the body by shutting down production.
Conversely, Tamoxifen limits the binding to receptors throughout the body. Unlike other variations of treatment, tamoxifen does not specifically target breast tissue. Rather it inhibits binding throughout the entire body. This leads to muscle soreness, cramps, and joint aches as water levels begin to deplete in the body. Unlike Anastrozole, tamoxifen does not deplete bone mineral levels.
E2 plays a key role in bone, skin, hair, and nail health among other things to include but not limited to libido and mood. Anastrozole shuts down estradiol indiscriminately and Tamoxifen blocks reception indiscriminately as well. So regardless of the type of estradiol you are battling with, AI's and SERMs affect them all. Anastrozole has a tendency to cause more long term side affects, but Tamoxfen boasts early onset of side affects. Patients more frequently complained about Tamoxifen sides, but long term they tended to opt to keep the Tamoxifen dose but changed from Anastrozole to other medications.
Estradiol is necessary in the body, and the root Estradiol is fast acting and very powerful. However, it splits into several subsects including; E2 2Hydroxyestrone E4 4Hydroxyestrone and E16 16Hydroxyextrone. 4 & 16 are both linked to cancers and terrible side affects. Controlling those two variations naturally is done through the consumption of dark leafy greens and fruits. The more diverse your diet and the more dark leafy greens you consume, the better. (See the blog on methylation).
Commentary and Recommendation
Those who are using other exogenous hormones like testosterone should be careful about running too many Aromatase inhibitors and SERMs as they come with consequences like thicker blood, high triglycerides, and loss of libido (among other things). Leveraging DHT androgens can help impede conversions without as many consequences, but they will not cease the production or binding of estradiol in its entirety. The best method is to start with a good diet, micro dosing your medical TRT, and leveraging DHT androgens for suppression before engaging aromatase inhibitors and SERMs.