I think it was more than 6 months ago when I found certain publications that Dr. Dror Paley had done research to find the effects of IGF-1 on lengthening of muscle. Refer to the post How Muscle Tissue Is Lengthened – Bone Lengthening Will Not Be Limited – Breakthrough!. In that post, I had revealed a Grant that Paley along with other limb lengthening surgery surgeons had proposed to study the effects of using IGF-1 during distraction osteogenesis surgery. (IGF-1 Gene Therapy of Muscle during Distraction Osteogenesis)
In that post, I had proven that the limitation that certain posters on the online forums have set forth, on the inability of muscle tissue to stretch, has also been worked out and had the technical problems resolved. The muscle factor has now been considered and worked around.
What I would propose fro Paley’s research is a personal theory. Here it is…
It might be that IGF-1 does not really help make the growth plates grow thicker and have the chondrocytes proliferate more. What might actually be happened is that the IGF-1 is having the most affect on the muscle tissue surrounding the growth plate, while it is still active.
If we assume that the IGF-1 which is injected into the leg close to the growth plate makes the muscle tissue in that area thicker, which I believe right now could translate to mean longer, then the tension on the bone in the center would decrease.
If we remember the studies which show that “periosteal stripping” would increase the rate of bone longitudinal growth, the surgeons who did those tests more than 100 years ago had suggested that if you just remove the elements that hold the growth plates in place (ie periosteum layer) then the inhibitory factors would be removed, allowing the functional growth plate to expand much more than expected.
If the periosteum is one of those factors, acting like a tough raincoat wrapped around the body which doesn’t allow the growth plate to push outwards, then the muscles which are bound in a certain length could be thought of as the other major factor (maybe also the ligaments and tendons that are connected to the bones might have also an effect).
Since the IGF-1 would increase the muscles, and thus make them longer, as Paley suggested, maybe the growth plates would feel less inhibited by that factor, and the bone in the middle of a limb grow longer as a result of the growth plate having the chance to push outwards a little more.
Comparing “races”: Based on the idea that different “races” have different levels of IGF-1 that is stimulated during puberty, I would even make the guess that the people who are African Americans have increased IGF-1 stimulation compared to the other race groups. (Refer to “Growth Hormone and Weight Gain in African-American Girls“) Studies show that the african american community have around a 15% increased rate for developing Diabetes Type II since the African American children have higher blood insulin levels.
From the study “Relationships Between IGF-1 and IGFBP-1 and Adiposity in Obese African-American and Latino Adolescents” I refer to the following passage…
” It has been shown that Latino and Caucasian prepubertal females have lower IGF-1 levels compared to African-American females (16,20). Other studies have reported positive correlations between total body fat and IGF-1 concentrations in Caucasian children (21,22) and our laboratory demonstrated a positive relationship between IGF-1 and body fat in African-American and Caucasian children that was not explained by diet, physical activity, socioeconomic status, or adiposity”
Does that mean then African American’s would end up taller than other races since the IGF-1 level is slightly higher? Not really, since we need to realize that the natural physiological way for IGF-1 to even be developed is for it to be converted from HGH in the pancreas. HGH does make the chondrocytes in the growth plate divide faster, but the HGH also speeds up the senescence and maturity of bone. Also, IGF-1 can also be sourced from other areas of the body besides just the organ where HGH had the transformation.
So at the same time IGF-1 would cause the muscles to “loosen up”, the elevated GH levels in the system would also speed the body towards ossification. This phenomena is noticed when we see the data showing that on average, African American Females start puberty about 0.5 years earlier than their Caucasian American counterpart. However, the age at which the body stops getting taller would also be earlier as well.
Mathematically speaking, if we say that the duration of puberty is the same for black and white adolescent, from 10.5-17.5, and 11-18 respectively, then it would mean that the ‘white’ groups would on average end up slightly taller, since they had about an extra 1/2 of a year to grow on average. Then when we add in the factor that elevated IGF-1 rates might give the growth plates more growing potential during a short duration of time (from having one of the inhibitory factors removed), in the peak puberty years, then it might turn out that on average, “white” and “black” americans would end up almost exactly the same in height when we average out the entire population and truncate the outliers.
The end result is that while the adult height for the two ethnic groups eventually end up to be almost the same, the adult African American ends up having a higher BMI from a higher adult weight, which is positively correlated with the levels of IGF-1 as detected when they were still an adolescent.