I'm having issues understanding this. Could somebody shed some light?
Sex hormone binding globulin is regarded as one of man's big bugaboos.
Here's why: In normal men, only about 2% of our Testosterone is "free," or unbound to carrier proteins. That means that presumably, only 2% is free to be ferried into cells to make muscle grow (among other things). About 54% is bound to albumin and other proteins, and 44% is bound to Sex Hormone Binding Globulin, or SHBG, which is synthesized by the liver.
For years, strength athletes have been trying to figure out how to reduce the amount of SHBG so that more free Testosterone was available for all the good stuff, like muscle growth.
However, as studies that have been largely ignored by the strength community have revealed, it seems that we might all be full of hooey.
For one thing, it now seems that red blood cells function as carriers of sex hormones in the blood stream, and in fact may be responsible for as much as 15% of sex hormone delivery to target tissues.(7) What happens is that dissociation of this protein-bound hormone can occur within a capillary bed, meaning that it's not just the "free stuff" that's working.
The amount of hormone that can be carried depends on capillary transit time, half time of dissociation, amount of hormone bound to various carrier proteins, and permeability of cell membrane.
That means that these binding proteins in circulation act as kind of a steroid bank. In fact, it's a lot like how hemoglobin regulates the amount of oxygen in each tissue.
(This may be why the free T levels of strength athletes always seem to come up quite low on blood tests. Obviously, they're functioning just fine, but judging by their levels of free T, you'd think they were Girl Scouts.)
Just curious because my Free test levels are rock bottom as well.