SERM Aromatise Inhibitor Basics
Selective Estrogen Receptor Modulator (SERM) Compounds that bind with estrogen
receptors and exhibit estrogen action in some tissues and anti-estrogen action
in other tissues. The ideal SERM would deliver all the benefits of estrogen
without the adverse effects. ex: Clomiphene Citrate (Marketed as Clomid or Serophene). Tamoxifen (Marketed as Nolvadex).
Aromatise Inhibitor (AI) Aromatase inhibitors exhibit a very different mechanism
of action than SERM's. Aromatase inhibitors prevent the conversion of androgens
into estrogen in fat, muscle, breast, and brain. ex: Anastrazole (brand name
Arimidex). FEMARA (letrozole tablets).
NOTE: Clomid and Nolvadex are both anti-estrogens belonging to the same group of
triphenylethylene compounds. They are structurally related and specifically
classified as selective estrogen receptor modulators (SERMs) with mixed
agonistic and antagonistic properties. This means that in certain tissues they
can block the effects of estrogen, by altering the binding capacity of the
receptor, while in others they can act as actual estrogens, activating the
receptor. In men, both of these drugs act as anti-estrogens in their capacity to
oppose the negative feedback of estrogens on the hypothalamus and stimulate the
heightened release of GnRH (Gonadotropin Releasing Hormone). LH output by the
pituitary will be increased as a result, which in turn can increase the level of
testosterone by the testes.
Although these two are related anti-estrogens, they appear to act very
differently at different sites of action. Nolvadex seems to be strongly
anti-estrogenic at both the hypothalamus and pituitary, which is in contrast to
Clomid, which although a strong anti-estrogen at the hypothalamus, seems to
exhibit weak estrogenic activity at the pituitary.
by William Llewellyn
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