Updated 10-09-07
Estrogen modulation is a growing target for bodybuilders. The goal is to either reduce levels of estrogen or reduce activity of estrogen receptors. This is a short review of various targets and drugs available. This will be updated and expanded as needed.
Aromatase inhibitors:
AIs are categorized into two types:
Type 1: Irreversible steroidal inhibitors such as exemestane form a permanent bond with the aromatase enzyme complex.
Type 2: Non-steroidal inhibitors (such as anastrozole, letrozole) inhibit the enzyme by reversible competition.
Aromatase inhibitors work by inhibiting the action of the enzyme aromatase, which converts androgens into estrogens by a process called aromatization. By inhibiting aromatase they increase Testosterone and reduce Gynecomastia.
1. Letrozole (name Femara) is a type 2.
Letrozole has shown to reduce estrogen levels by 98 percent while raising testosterone levels. The anti-estrogen action of letrozole is preferred by bodybuilders for use during a steroid cycle to reduce bloating due to excess water retention and prevent the formation of gynecomastia related breast tissue that is a side effect of some anabolic steroids. Usage above 2.5 mg/day is known to potentially temporarily kill sex drive. Above 5mg/day for extended periods may cause kidney problems.
2. Vorozole (yet to be approved) is a type 2.
3. Exemestane (Aromasin) is a type 1.
Exemestane is an irreversible, steroidal aromatase inactivator, structurally related to the natural substrate androstenedione. It acts as a false substrate for the aromatase enzyme, and is processed to an intermediate that binds irreversibly to the active site of the enzyme causing its inactivation, an effect also known as "suicide inhibition." In other words, the Exemestane, by being structurally similar to the target of the enzymes, permanently binds to those enzymes, thereby preventing them from ever completing their task of converting androgens into estrogen.
The estrogen suppression rate for exemestane varies from 85% to 95%.
4. Anastrozole (Arimidex) is a type 2.
While officially indicated for women, this drug has proven effective in the off-label use of reducing estrogens (in particular and more importantly, estradiol) in men. Excess estradiol in men can cause benign prostatic hyperplasia, gynecomastia, and symptoms of hypogonadism. Some athletes and body builders will also use anastrozole as a part of their steroid cycle to reduce and prevent symptoms of excess estrogens; in particular, gynecomastia and water retention.
Study data currently suggests that dosages of 0.5mg to 1mg a day reduce serum estradiol by about 50% in men
SERM (Selective Estrogen Receptor Modulaters):
Are a class of compounds that acts on the estrogen receptor. A characteristic that distinguishes these
substances from pure receptor agonists and antagonists is that their action is different in various tissues, thereby granting the possibility to selectively inhibit or stimulate estrogen-like action in various tissues
1. Tamoxifen (brand name Nolvadex).
In men, tamoxifen is sometimes used to treat gynecomastia which arises for example as a side effect of antiandrogen prostate cancer treatment. Tamoxifen is also used by bodybuilders to prevent or reduce drug-induced gynecomastia caused by the estrogenic metabolites of anabolic steroids.
2. Clomifene or clomiphene (brand name Clomid)
Clomifene acts by inhibiting the action of estrogen on the gonadotrope cells in the anterior pituitary gland. In response to low estrogen levels, follicle-stimulating hormone (FSH) release is increased. Clomifene is commonly used by male anabolic steroid users to bind the estrogen receptors in their bodies, thereby blocking the effects of estrogen, i.e., gynecomastia. It also
restores the body's natural production of testosterone. It is commonly used as a "recovery drug" and taken toward the end of a steroid cycle.
3. Toremifene citrate (brand name Fareston).
4. Raloxifene (brand name Evista).
5. Bazedoxifene (brand name Viviant).
SERD (Selective Estrogen Receptor Downregulator):
Also called a Pure Antiestrogen.
1. Fulvestrant (brand name Faslodex) It is an estrogen receptor antagonist with no agonist effects, which works both by down-regulating and by degrading the estrogen receptor. In some studies it is stronger than anastrozole.
