IGF-1 is a peptide
roughly the same structure and size as insulin
, or about
70 amino acids long. It belongs to the peptide family of substances
identified as growth factors. It is a highly anabolic hormone released
in the liver as well as in peripheral tissues such as skeletal muscle.
In the body, IGF-1
is released in response to the presence of Human
After intense resistance training, the body experiences a surge in GH
and IGF, and this is one way that new muscle is built. Although GH
is considered to be highly anabolic, in actuality, IGF-1 is suspected
to be responsible for the primary anabolic activities of GH.
builds new muscle tissue by promoting nitrogen retention and protein
synthesis. This causes the growth of muscles through both hyperplasia
(which is an increase in number of muscle cells) and mitogenesis (which
is the actual growth of new muscle fibers). Thus IGF-1 not only makes muscle
fibers bigger, it makes more of them as well!
IGF-1ís effects are not limited to building new muscle, however. It has
a potent effect on lipid (fat) metabolism, and helps the body burn fat
at a significantly elevated rate. In addition, IGF-1 is both a
neuroprotector and neuropromotor, which improves mental functions such
as reflexes, memory, and learning ability. IGF is also important for
production of connective tissue and
insuring proper bone density.
Although IGF-1 is very potent at building muscle and burning fat, the
Lr3 IGF-1 version is roughly 2-3x as powerful.
Lr3IGF-1 (Long R3
Insulin-like Growth Factor-I or Long R3IGF-I
) is an 83 amino acid analog of human
IGF-I actually comprising the complete human IGF-1
sequence but with the substitution of an Arg for the Glu at position 3,
as well as a 13 amino acid extension peptide at the N-terminus. This
makes Long R3IGF-I significantly more potent (2-3x) than IGF-I in
studies, because it has a lower affinity to be rendered inactive by IGF
binding proteins, and consequently more potential activity in the body.