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by Anthony Roberts -- Aromasin (Exemestane)
is one of those weird compounds that nobody really
knows what to do with. What we generally hear about
it makes it very uninteresting…It’s a third generation
Aromatase Inhibitor (AI) just like
Arimidex (Anastrozole)
and Femera (Letrozole).
Both of those two drugs are very efficient at stopping
the conversion of androgens into estrogen, and since
we have them, why bother with Aromasin? It’s a little
harder to get than the other two commonly used aromatase
inhibitors, because it’s not in high demand, and
there’s never been a readily apparent advantage
to using it. And I mean…lets face it: It’s awkward-sounding.
Aromasin doesn’t have much of a ring to it, and
exemestane is even worse. Arimidex has a bunch of
cool abbreviations ("A-dex" or just ‘dex) and even
Letrozole is just "Letro" to most people. Where’s
the cool nickname for Aromasin/exemestane? A-Sin?
E-Stane? It just doesn’t work. It’s the black sheep
of AIs. And why do we even need it when we have
Letrozole, which is by far the most efficient AI
for stopping aromatization (the process by which
your body converts testosterone into estrogen)?
Letro can reduce estrogen levels by 98% or greater;
clinically a dose as low as 100mcgs has been shown
to provide maximum aromatase inhibition (2)! So
why would we need any other AIs? Well, first of
all, estrogen is necessary for healthy joints (3)
as well as a healthy immune system (4). So getting
rid of 98% of the estrogen in your body for an extended
period of time may not be the best of ideas. This
may be useful on an extreme cutting cycle, leading
up to a bodybuilding contest, or if you are particularly
prone to gyno, but certainly can’t be used safely
for extended periods of time without compromising
your joints and immune system.
So that leaves us with Arimidex, which isn’t
as potent as Letrozole, but at .5mgs/day will still
get rid of around half (50%) of the estrogen in
your body. Problem solved, right? Use Arimidex on
your typical cycles, and if you are very prone to
gyno or are getting ready for a contest, use Letro.
But what about Post Cycle Therapy (PCT)?
I think at this point most people are sold on
the use of Nolvadex (Tamoxifen
Citrate) instead of Clomid
for PCT, since both compete estrogen at the receptor
site, both increase serum test levels, and both
drugs may also alter blood lipid profiles favorably
(6). But since 20mgs of Tamoxifen is equal to 150mgs
of clomid for purposes of testosterone elevation,
FSH and LH, but Tamoxifen doesn’t decrease the LH
response to LHRH (6) I think most people agree to
Nolvadex’s superiority for PCT.
I’ve always been in favor of using Nolvadex during
PCT, along with an AI, because reducing estrogen
levels has been positively correlated with an increase
in testosterone (7) so in my mind, it’s be beneficial
to increase testosterone by as many mechanisms as
possible while trying to recover your endogenous
testosterone levels after a cycle. SO which AI do
we use? Letro or A-dex? Well, why don’t we just
keep using whichever one we used during the cycle,
and add in some Nolvadex? Unfortunately, Nolvadex
will significantly reduce the blood plasma levels
of both Letrozole as well as Arimidex (8). So if
we choose to use one of them with our Nolvadex on
PCT, we’re throwing away a bit of money as the Nolvadex
will be reducing their effectiveness.
This, of course, is where Aromasin comes in,
at 20-25mgs/day.
Aromasin, at that dose, will raise your testosterone
levels by about 60%, and also help out your free
to bound testosterone ratio by lowering levels of
Sex Hormone Binding Globulin (SHBG), by about 20%
(12)…SHBG is that nasty enzyme that binds to testosterone
and renders it useless for building muscle. But
what about using it along with Nolvadex for PCT?
To understand why Aromasin may be useful in conjunction
with Nolvadex while both Letro and A-dex suffer
reduced effectiveness, we’ll need to first understand
the differences between a Type-I and Type-II Aromatase
Inhibitor. Type I inhibitors (like Aromasin) are
actually steroidal compounds, while type
II inhibitors (like Letro and A-dex) are non-steroidal
drugs. Hence, androgenic side effects are very possible
with Type-I AIs, and they should probably be avoided
by women. Of course, there are some similarities
between the two types of AIs…both type I & type
II AIs mimic normal substrates (essentially
androgens), allowing them to compete with the substrate
for access to the binding site on the
aromatase enzyme. After this binding, the
next step is where things differ greatly for
the two different types of AI’s. In the case of
a type-I AI, the noncompetitive inhibitor
will bind, and the enzyme initiates a sequence
of hydroxylation; this hydroxylation produces an
unbreakable covalent bond between the
inhibitor and the enzyme protein. Now, enzyme activity
is permanently blocked; even if all unattached inhibitor
is removed. Aromatase enzyme activity
can only be restored by new enzyme synthesis. Now,
on the other hand, competitive inhibitors, called
type II AI’s, reversibly bind to the active enzyme
site, and one of two things can happen: 1.)
either no enzyme activity is triggered or 2.) the
enzyme is somehow triggered without effect.
The type II inhibitor can now actually disassociate
from the binding site, eventually allowing renewed
competition between the inhibitor and the substrate
for binding to the site. This means that the
effectiveness of competitive aromatase inhibitors
depends on the relative concentrations and affinities
of both the inhibitor and the substrate, while
this is not so for noncompetitive inhibitors. Aromasin
is a type-I inhibitor, meaning that once it has
done its job, and deactivated the aromatase enzyme,
we don’t need it anymore. Letrozole and Arimidex
actually need to remain present to continue their
effects. This is possibly why Nolvadex does not
alter the pharmacokinetics of Aromasin (11).
Before we close the book on Aromasin, it’s worth
noting that you can (and should) still use one of
the non-steroidal AIs during your cycle to reduce
estrogen, if necessary. When you are ready for PCT,
you can then switch over to Aromasin and still experience
the full effects of an AI, since there is no cross-over
tolerance experienced between steroidal and non-steroidal
AIs (9). Since Aromasin is about 65% efficient at
suppressing estrogen (10), it’s certainly a very
powerful agent, especially considering you won’t
experience reduced effectiveness because of your
concurrent use of Nolvadex or from any sort of tolerance
developed by using other AIs on your cycle(9). There
is also a decent amount of preclinical data suggesting
that Aromasin has a beneficial effect on bone mineral
metabolism that is not seen with non-steroidal
agents, and it may also have beneficial effects
on lipid metabolism that are not found
in the non-steroidal Letro and A-dex (9).
Finally, as we’re going to be using Nolvadex
for PCT anyway, and we ought to be using an AI with
it for maximum recovery…I think Aromasin- considering
it’s compatibility with Nolvadex and beneficial
effects on bone mineral content and lipid profile,
has finally stopped being the black sheep of AIs
and found a home in our Cycles.
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