An increase in SHBG (its SHBG not SBGH) results in a decrease in free test, not an increase. Sexual Hormone Binding Globulin binds to the hormone , rendering less of it active. The more SHBG, the less active hormone.[/QUOTE
]From the Iron Mag research article:
When discussing IGF-1 within the context of muscle growth, most tend to focus on the level of this hormone in the bloodstream, while paying little to no attention to those factors which influence the ability of IGF-1 to do its job. One of these is IGF-1 binding protein 3, or IGFBP-3, for short. While low dosages of MK-677 (5 mg/day) do not increase levels of this protein, normal dosages (25 mg/day and above) do. For many of you reading this, your initial reaction may be to think of this as a negative trait, due to misconceptions surrounding the role of sex hormone binding globulin (SHBG) in testosterone metabolism, but the truth is that elevations of IGFBP-3 (as well as SHBG, for that matter) are a good thing.
Let’s use testosterone as an example. Once testosterone has entered the bloodstream, it resides in one of two forms—in either a free or bound state. Free testosterone circulates as is, while bound testosterone is testosterone which has been bound to SHBG. For decades, most people thought, even the medical community, that free testosterone was all that mattered, as bound testosterone was believed to be unusable by the body; held hostage by SHBG. We now know we were wrong, as SHBG is not the enemy after all, but functions as transporter protein, helping to usher testosterone to the receptor site where it can then perform its actions.
In the same way, IGFBP-3 is the main carrier of IGF-1, but IGFBP-3 is more than just a transporter. It also helps prolong the life of IGF-1 in the body. In other words, the more IGFBP-3 present, the better. So, MK-677 not only increases growth hormone and IGF-1 levels, but also IGFBP-3, further potentiating the positive effects of IGF-1 on muscle growth.