Free v Bound Testosterone: What’s The Difference?

Free testosterone

Extracted from Your New Prime – 30 Days to Better Sex, Eternal Strength, and a Kick-Ass Life After 40

If you get your T levels tested, you’ll probably get a slew of numbers: total, bio-available, and free. What do these numbers mean?

Hormones act like commuters on a train: they circulate through the bloodstream, where they are often linked to other substances, then they get off when they reach their target tissues (like muscle and bone) where they are to perform their particular function.

Most of the time, T hitches a ride on something called sex hormone-binding globulin (SHBG). Less frequently, it binds itself to another substance called albumin, and still less often, it bodysurfs through your system solo.

As you probably can guess, “total” T represents all the testosterone in your system in any state—bound to SHBG, bound to albumin, and all by its lonesome. “Free” T is the stuff that’s on its own. “Bio-available” T is a measure of free testosterone combined with the T that’s bound to albumin. Generally speaking, about 65 percent of the testosterone in the blood binds to SHBG, 30 to 40 percent binds with albumin, and about 2 percent is free.

Here’s where it gets tricky (and relevant to a guy trying to boost his sex drive, energy, and muscle-building potential): only the bio-available T—the free T plus the albumin- bound stuff—really matters. That’s because when T is bound to SHBG, it can’t jump off and do its job on the target tissue: it’s as if it’s handcuffed to the commuter train.

The difference between “bio-available” T and “total” T is a bit like the difference between body fat percentage and total weight. You might weigh a healthy sounding 180 pounds, but if 33 percent of that is body fat, you’re definitely less than healthy.

So another way to effectively increase your T is to unleash a greater percentage of it from the SHBG that keeps it corralled. And lucky for you, this book includes several methods of doing just that.

Read more in my book, Your New Prime – 30 Days to Better Sex, Eternal Strength, and a Kick-Ass Life After 40.


by Mens Health Editor

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