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Anti-Estrogens And IGF-1 Production
GH (Growth Hormone) is like a master hormone for tissue growth and fat regulation due to its own intrinsic qualities and its propensity to be converted into or trigger the production and release of Growth Factors. Of these Growth Factors, one of the best known in regard to muscle growth is IGF-1 (Insulin-Like Growth Factor-1).
As most are aware by now, IGF-1 is a powerful anabolic and anti-catabolic hormone. Whether in pre-contest mode or packing on the mass, the amount of circulating and stored IGF-1 an athlete maintains plays a powerful role in the results achieved. Obviously as IGF-1 levels decrease so does the potential for packing on the beef, and the amount of lean tissue lost during calorie-restricted periods increases as well. (Not good)
Estrogen, and more so estradiol, can trigger GH release from the pituitary gland. Aromatase inhibitors decrease the amount of circulating estrogen/estradiol and estrogen receptor antagonist keep estrogen out of the specific pituitary receptors. So in many regards the use of anti-estrogens can effect IGF-1 production and in some cases affect the number of IGF-1 receptors our tissues posses.
Product Effect Percentage
Formestane/4-Androstenoldione Increases IGF-1 26%
Femara/Letrozol Increases IGF-1 24%
Cytadren/Aminoglutethimide Increases IGF-1 27%
Aromasin/Exemestane Increases IGF-1 28%
Arimidex/Anastrozole Decreases IGF-1 18%
Nolvadex/Tamoxifen Decreases IGF-1 23.5%
Faslodex/Fulvestrant Decreases IGF-1 70%
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