Insulin-Like Growth Factor 1
Pharmaceutical Name: Insulin-Like Growth Factor 1
Drug Classification: Polypeptide Hormone
Active Life: huIGF-1: approximately 10 minutes, Long R3 IGF-1: 2-5
hours
Insulin-Like Growth Factor-1 (IGF1) is a polypeptide protein hormone that is
one of the primary substances that is responsible for tissue growth in humans,
including muscle growth (1). IGF1 is primarily secreted by the liver, with a
small minority of the circulating amount of the hormone being produced and
delivered by other tissues. The basic function of the hormone is to induce
cellular activities. For bodybuilders and strength athletes this compound
could produce good results when used due to the ability of the compound to
potentially enhance muscle hyperplasia, the actual increase in number of
muscle cells in the body or particular muscle.
This effect of muscle hyperplasia that IGF1 can help promote is the primary
reason why it has become so popular among bodybuilders. It is believed that
IGF1 may be able to produce localized growth in the muscles that the IGF1 is
administered into post-workout. However this effect of the hormone remains
more theoretical in nature because of the lack of research available on the
subject using human subjects. Despite this many users still claim that they
have seen results from IGF1 when using it for this explicit purpose and it
remains within the realm of possibilities. However simply because science can
not discount the result as implausible does not mean that it is a given
either.
Among the other anabolic effects that IGF1 can produce in the body are things
such as increasing protein synthesis, increasing nitrogen retention, as well
as inducing the growth of more muscle fibers. When an appropriate amount of
amino acids (protein) is available, all of these actions within the body are
able to be completed. It has been demonstrated that IGF1 can help to improve
collagen production as well as the reproduction of cartilage in joints (2).
The hormone has also been shown to exhibit the ability to act as a
neuro-protector and promoter (3) mainly because IGF1 receptors are located in
the tissue of the brain (4). It has been demonstrated that there is a
potential for when supplemented with IGF1 a decrease in the progress of some
brain diseases can be brought about as well as slowing the deterioration of
brain function in some elderly subjects. However similar findings or any
evidence of improved brain function or capacity has not been demonstrated in
young, healthy individuals.
Obviously by helping to promote these anabolic mechanisms for growth IGF1 also
acts as an anti-catabolic. This would be beneficial to those users in a
calorie deficit or in other circumstances that place them at risk of losing
muscle mass. IGF1 also has the ability to positively affect lipolysis in users
if other necessary conditions are met, namely proper diet and training
protocols. When combined with the ability to preserve muscle mass, IGF1
appears to be an attractive choice for those that are attempting to decrease
their body fat while maintaining as much of their muscle mass as possible.
IGF1 is composed of seventy amino acids, the same number as insulin. As stated
earlier, it is primarily secreted by the liver. The stimulus that is
responsible for this secretion is the presence of growth hormone. In fact IGF1
is primarily the causal connection between growth hormone and its anabolic and
anti-catabolic capabilities. This is not to say that effects caused by growth
hormone could be produced with only IGF1, but rather that the two compounds
are very much related to one another and both are needed for optimal tissue
growth.
In some animal studies there have been significant findings that support the
idea that IGF1 administration can help to induce large increases in both
strength and muscle size. While these results have not been reproduced in
humans they do suggest that the gains experienced by users are connected to
the administration of IGF1 and related to the anabolic mechanisms that are
caused by the hormone. However to say that the findings of some of these
studies could be replicated in humans would be incorrect. For example, a
twenty-seven percent increase in muscle strength was produced in mice advanced
in age when administered moderate dosages of IGF1 (5). Of course it would be
dubious to claim that similar gains could be made by a trained athlete that
chose to use IGF1 but it does suggest that the hormone will promote at least
some of the mechanisms responsible for muscle growth.
As stated, the IGF1 produced by the human body is seventy amino acids in
length. However a different IGF1 composition is available. Called Long R3
Insulin-Like Growth Factor-1 (LR3 IGF1), it has the original seventy amino
acids of regular IGF1 with a substitution of Arginine in place of Glutamic
Acid at position three in the sequence. Additionally thirteen more amino acids
have been added to the sequence. This extension peptide is located at the
N-terminus in the sequence. These alterations were made so that the hormone
would be more likely to remain active and potent when it encounters
Insulin-Like Growth Factor-1 binding proteins in the body (6). All of this
adds up to LR3 IGF1 being potentially three times as potent as the regular
version of IGF1, or human IGF1 (huIGF1). Obviously this makes LR3 IGF1 more
attractive for strength athletes and bodybuilders. For this reason it is now
the most widely available version for purchase due to the compound having all
of the benefits of regular IGF1, and being potentially three times as potent,
while having no additional risks or side effects to that of regular IGF1.
Use and Dosing of IGF-1
Depending upon which form of IGF1 which a person is administering, the dosing
will differ slightly. For huIGF1 dosing users will want to inject the drug
post-workout, most likely in the muscle(s) that was worked out to help produce
any potential local site growth if any is indeed possible. Due to the
extremely short active life of the drug users will likely want to inject the
drug several times to help and prolong the effects of the drug. Splitting the
dose into two to four injections should be sufficient. When administering the
compound on days where the user does not work out a similar dosing protocol
could be used in any of the muscles that the user desires.
For LR3 IGF1, because of the longer active life of the drug in comparison to
huIGF1, users will not have to administer the drug as frequently. Twice daily
injections should be sufficient, although a single injection daily should also
be able to produce significant results for the majority of users. Again, users
will want to inject the drug post-workout in the muscle(s) that were worked.
However, a second injection should be done elsewhere in the day. If not, a
single injection time post-workout should be used. On off days from the gym,
as with huIGF1, an injection can be made and may best be administered in the
morning as to best fight off muscle catabolism. Barring this, any convenient
time in the day can be used. However there are those users who simply opt not
to administer any IGF1 on non-training days. It is at the discretion of the
user.
Due to the possible local site growth that IGF1 may induce in users, many will
split their doses and inject bilaterally. That is to say inject half of the
dose into the muscle on the left side of their body and the other half of the
dose in the right side of their body. Alternatively the user can simply inject
the entire dose of IGF1 in one muscle on one day while making sure to inject
the other muscle with the entire dose the next time that that muscle group
falls in the injection rotation of the user.
The duration that a user will want to run IGF1 for is determined by the fact
that IGF1 receptors in the body become saturated as large amounts of the
hormone are introduced into the body. As the use of IGF1 continues, these
receptors will begin to downgrade and the effects of the hormone will begin to
lessen. For this reason consistent breaks from use of IGF1 need to be taken by
users. Anecdotally the majority of users report seeing their gains from IGF1
begin to diminish after using the drug for about four to six weeks. This would
seemingly indicate that receptor downgrade would be happening around this
mark. However there is little to no information regarding IGF1 receptor
downgrade and exactly how long it takes to occur and how long it takes for
these receptors to recover. We are left to decipher these personal experiences
with the drug and extrapolate the most efficient way to use it. As stated, it
seems that cycles of about four to six weeks are ideal for many users although
longer cycles are certainly possible. When coming off of the compound an equal
amount of time spent off of it as was spent using it seems to allow for the
IGF1 receptors to �upgrade� and once again be able to produce the results the
user experienced initially. However despite these assumptions there are
countless theories and protocols that users may administer IGF1 with and if
they find it beneficial then there is no reason not to use these alternative
protocols. There is simply not enough research to make definitive statements
about how best or how long to run this drug.
In terms of dosing for huIGF1, users have reported seen good results when
administering dosing ranging from 100 to 160 mcg per day. This total dose
would be split into several injections, most of which would likely be
administered post-workout. For LR3 IGF1, the generally excepted or reported
range for dosing is seemingly between 40 to 120 mcg per day. Again however due
to the lack of research concerning IGF1 and its use in athletes these dosages
are composed of through the collection of anecdotal evidence from users and
not scientific research.
Risks and Side Effects while using IGF-1>
Beyond the natural downgrading of the IGF1 receptors when using exogenous
IGF1, there are appears to be little in the way of significant risks to the
health of the user associated with its use. Caution has to be used when saying
this however again due to the lack of empirical research conducted using this
drug on human subjects.
One major risk that could potentially become problematic for some users is the
ability of IGF1 to promote or enhance the growth of pre-existing tumors and
cancers (1). Similarly to growth hormone, IGF1 can
accelerate the growth of tumors which is not to be unexpected due to the very
nature of IGF1 as a growth factor within the body and the effect it has on
cells. For this reason it is advisable that prior to undertaking use of IGF1 a
user gets medically cleared by a doctor and ensures that no tumors or other
diseases that could be exasperated by use of the drug are present.
A far less potentially severe side effect of IGF1 use is the suppression of
the endogenous human growth hormone production in users. Endogenous IGF1
creates a negative feedback loop for growth hormone in humans. Exogenous IGF1
will have the same effect and therefore will likely cause growth hormone
production to be temporarily suppressed in users. This is another reason why
users will want to cycle their use of IGF1 and not attempt to stay on the drug
for extended periods of time. By limiting the use of IGF1 to only a few weeks,
this should ensure the general health of the user as well as the mechanism
responsible for the production of both IGF1 as well as human growth hormone.
While not being significant, IGF1 also has the ability to lower blood glucose
levels. For the most part the compound will not lower the blood glucose in
users to dangerous levels unless a pre-existing condition is evident. However
this lowering of blood glucose will often cause the user to feel lethargic.
This sometimes lasts the duration of use of the drug but should subside once
the administration of the compound ceases.
A trait that again is shared with human growth hormone is the fact that use of
IGF1 sometimes results in users having aches and pains form most notably in
their wrists, fingers and hands. This is a common side effect but if it
becomes unbearable a lowering of the dosage should reduce the severity of the
symptoms. They will cease once administration of the drug is discontinued.
In addition, while it is possible that IGF1 could cause abnormal organ growth
and/or acromegaly it would simply take overly large doses used for long
durations of time for this to occur in users. With normal use of the drug
these side effects should not be a concern for the vast majority of users
however.
References
1. Smith GD, Gunnell D, Holly J. Cancer and insulin-like growth
factor-I. A potential mechanism linking the environment with cancer risk. BMJ.
2000 Oct 7;321(7265):847-8.
2. Sienkiewicz P, Palka M, Palka J. Oxidative stress induces IGF-I receptor
signaling disturbances in cultured human dermal fibroblasts. A possible
mechanism for collagen biosynthesis inhibition. Cell Mol Biol Lett.
2004;9(4A):643-50.
3. Mendez P, Azcoitia I, Garcia-Segura LM. Interdependence of oestrogen and
insulin-like growth factor-I in the brain: potential for analysing
neuroprotective mechanisms. J Endocrinol. 2005 Apr;185(1):11-7.
4. Creyghton WM, van Dam PS, Koppeschaar HP. The role of the somatotropic
system in cognition and other cerebral functions. Semin Vasc Med. 2004
May;4(2):167-72.
5. Barton-Davis ER, Shoturma DI, Musaro A, Rosenthal N, Sweeney HL. Viral
mediated expression of insulin-like growth factor I blocks the aging-related
loss of skeletal muscle function. Proc Natl Acad Sci U S A. 1998 Dec
22;95(26):15603-7.
6. Walton PE, Dunshea FR, Ballard FJ. In vivo actions of IGF analogues with
poor affinities for IGFBPs: metabolic and growth effects in pigs of different
ages and GH responsiveness. Prog Growth Factor Res. 1995;6(2-4):385-95.
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