
Aromasin (Exemestane) is a
Type-I aromatase inhibitor, or suicidal
aromatase inhibitor. It’s called this because it lowers estrogen
production in the body by attaching to the aromatase enzyme, and
permanently deactivating it.
[1]
Personally, I find this to be a
very interesting mechanism of action when compared to type-II aromatase
inhibitors, which bind competitively to the aromatase enzyme, and
eventually unbind, rendering it active again. In the case of Aromasin,
this doesn’t happen, and once it does its job on the enzyme, those
particular enzymes will no longer function. Your body will eventually
create more of the aromatase enzyme, so this isn’t dangerous, despite
the really odd “suicide” thing in the first paragraph. As with all
aromatase inhibitors, Aromasin was developed to fight breast cancer
primarily in post-menopausal women, but we in the athletic community
use it to combat estrogenic side effects from aromatizable steroids, or
for post cycle therapy.
Estrogen is responsible for many of the effects we’re trying to avoid
when we’re on a cycle, including excess water retention and development
of gynocomastia (breast tissue development in males. Thus, limiting the
conversion of
testosterone
into estrogen is of use for steroid using athletes, when they’re trying
to avoid side effects. In this case, the advantage of using a suicidal
aromatase inhibitor is that it really won’t cause much, if any,
noticeable “rebound” in estrogen when you cease using it.
The hard numbers on Aromasin are reasonably impressive, as it averages
an 85% rate of estrogen
suppression
[2],
and this translates to an overall reduction in
estradiol levels of about 50%, as well as raising testosterone to a
significant degree.
[3].
It is also known as a “steroidal” aromatase inhibitor. This is really
interesting, because it has been known to actually cause side effects
(androgenic sides) that include increased aggressiveness and a pretty
decent hardening effect.
[3]
I wouldn’t usually suggest that women
should use Aromasin in large doses for any extended period of time, for
this reason (possible virilization, or development of male sexual
characteristics could occur with its use). It should, therefore, be
reserved for use by women to brief periods of time in a possible
pre-contest phase or for a form of post cycle therapy after a cycle.
Fig 1. Aromasin vs. Nolvadex
Comparison
Interestingly (and almost paradoxically) exemestane not only increases
testosterone and lowers estrogen, but it also increases levels of
insulin-like growth Factor (IGF).
[5]
I find this to be interesting,
because although the rise in testosterone is most likely responsible
for the increase in IGF levels, IGF is known to be an aggravating
factor in the growth of breast tumors, like the kind found in breast
cancer. However, since estrogen is the primary culprit in breast
cancer, the large reduction in estrogen levels, even when combined with
a rise in
IGF, is enough to make Aromasin a very effective
breast
cancer medication.
Aromasin isn’t too harsh on blood lipids
[6]
(cholesterol), unlike some
of the other AIs’ like Letrozole.
Exemestane reaches steady blood plasma levels of after a week of
administration and this is also when we see it begin its maximal effect
on reducing circulating estrogen levels. It’s also has a ½ life of 27
hours
[4],
so taking it once per day is going to build up blood plasma
levels to a very effective level.