Bioavailable T

[Helboi]

So I was listening to a talk by Dr. Robert Carlson (heart surgeon) about TRT and the heart and he talked quite a bit about bioavailable T and why it's more important than Free T. Basically, from what I understood, bioavailable T is what you have after SHBG does its work, and free T doesn't take that into account. Is that correct? Is this an important marker to be tracking?

He uses this tool to calculate bioavailable T: http://www.issam.ch/freetesto.htm

I calculated mine using my last blood test and here are my results for bioavailable T: 688 ng/dL = 60.5 %

He mentioned in the video that he likes to see it from 400-600 and even higher in some cases, depending on the man. So, based on that, I'm sitting pretty good (which matches the way I feel, for sure).

 

[James]

James said:
Today 03:52 PM
I think bio available includes the testosterone that is bound by albumin, Which is far less tight than SHBG. I haven't seen a lot of albumin conversations on these boards. It's available if needed, but I don't know a whole lot about albumin.

 

[CoastWatcher]

Most circulating testosterone is bound to sex hormone-binding globulin (SHBG). A lesser fraction is albumin-bound, and a small proportion exists as free testosterone. Historically, only the free testosterone was thought to be the biologically active component. However, testosterone is weakly bound to serum albumin and dissociates freely in the capillary bed, thereby becoming available for tissue uptake. All non-SHBG-bound testosterone (the albumin-bound and the free testosterone) is therefore considered bioavailable.

 

[Helboi]

All non-SHBG-bound testosterone (the albumin-bound and the free testosterone) is therefore considered bioavailable.

So bioavailable T is just another way of looking at Free T? If so, I wonder why this doctor was so hip on bioavailable T as a good indicator to go by.

 

[CoastWatcher]

So bioavailable T is just another way of looking at Free T? If so, I wonder why this doctor was so hip on bioavailable T as a good indicator to go by.

No, that's not what I wrote. All non-SHBG-bound testosterone is considered bioavailable...meaning free testosterone (non-bound) and the testosterone weakly bound to albumin is considered bioavailable. By the way, that calculator is a good tool and can also be found in a "sticky post" here on the Forum.