Stopping HGH and IGF Levels

[griffinannie]

Doanyone know as to how long serum IGF levels will be elevated by hgh administration after stopping therapy. Thanks

[marianco]

Originally Posted by griffinannie

Doanyone know as to how long serum IGF levels will be elevated by hgh administration after stopping therapy. Thanks

There is a lot of unclarity in the literature.

As far as I know:

Growth hormone lasts perhaps 3-6 minutes in the bloodstream.

During that time, it triggers the production of IGF-1 in the liver. IGF-1 is suppose to be a longer lacting and the primary active version of growth hormone in the body (though growth hormone itself has direct effects of its own).

However, Free IGF-1 has a half-life of about 4.5 minutes. Thus it is active for about 22 minutes.

IGF-1 becomes bound to various binding proteins. The primary binding protein is IGF-BP-3.

These binding proteins prolong the half-life of IGF-1 - just like SHBG prolongs the half-life of Testosterone (Free Testosterone has a half-life of about 10-100 minutes).

Depending on the binding protein, the estimates of the half-life of bound IGF-1 varies between 6-20 hours with a common estimate of between 12-15 hours.

Assuming the half-life of bound IGF-1 is 15 hours, then IGF-1's activity is prolonged over baseline by the addition of growth hormone approximately 75 hours.

Assuming the half-life of bound IGF-1 is 6 hours, then IGF-1's activity is prolonged over baseline by the addition of growth hormone approximately 30 hours.