"Free and Weakly Bound Testosterone" vs. "Free Testosterone"

[ZenFitness]

Hi all,

I have some bloodwork this Friday and am going to bring in a couple of extra LabCorp test codes to add to the test. In looking for the Free Testosterone code, I noticed there are two:

Free Testosterone
Free and Weakly Bound Testosterone

Does anyone know the difference here?

[HRTstudent]

testosterone can bind to things such as albumin and shbg, maybe others. I'm not sure on all the specifics. and for practical purposes that is "okay" as it doesn't really matter. in fact, the entire notion of "free" testosterone vs total testosterone is very debatable and certainly not unequivocal. in fact, many good doctors and experts do not even bother with free testosterone.

having said that, i believe that testosterone bound to albumin is a weak bond. a weak bond in this fashion would mean that the testosterone might appear "bound" but it might change readily to an unbound form.

I wouldn't get too bogged down in this to be frank. getting your testosterone to the mid range around 650 and then stick with that while addressing other health problems.

this is, of course, my non-MD opinion .

[Lockout888]

Here ya go:

Testosterone , Free and Weakly Bound

Description: Free and weakly bound testosterone (FWBT), also referred to as bioavailable testosterone, is thought to reflect an individual's biologically active, circulating testosterone. FWBT includes free testosterone and testosterone that is bound to albumin. FWBT does not include sex hormone binding globulin-bound testosterone. The SHBG-bound fraction is biologically inactive because of the high binding affinity of SHBG for testosterone. The rapid dissociation of “weakly bound” testosterone from albumin results in the availability of essentially all albumin-bound testosterone for steroid-receptor interaction.

[HRTstudent]

we now "know" or believe that shbg-bound testosterone is not actually inactive now. that's the biggest departure I can see from that excerpt.