Importance of FREE Test?...........

[SugarMouth]

When talking to my doc about my lab results he mentioned my total test being on the lower side but was more impressed by the lack of free test. He mentioned free test being important.

I read through threads here and see little talked about with free test but constantly talking about total test. How important is the free number?

 

[halfape211]

Most of the testosterone in the blood is bound to a protein called sex hormone binding globulin (SHBG). Testosterone that is not bound ("free" testosterone). It is the free testosterone that our body uses to build muscle, etc. So in a way, I consider it to be very important. For some reason most people and doctors use TT as a scale to measure T.. Some clinics do use the free T as their guideline.

 

[Mprtz]

Opinions vary widely on this. Some will say that free test is what's really important.

From my reading, I'm not sure I agree. What exactly happens to free and bound testosterone at receptor sites doesn't seem to be completely understood.

Free test seems to vary more than total test due to fluctuating levels of SHBG and perhaps other factors. Free testosterone is more expensive to measure. I don't think it's a better candidate than total test for assessing your TRT dose.

Anecdotally, I've had free test 3x or 4x over top of range and didn't feel any different.

There are guys who have naturally low SHBG and they often report poor response to TRT - this would seem to contradict the assumption that high free test is what it's all about.

 

[Mprtz]

I think there's a case to be made for the role of SHBG as a type of buffering agent for testosterone which keeps it from being eliminated. Why would the body produce one substance, then another that binds to it and renders it inert?

Supraphysiological levels of testosterone frequently lead to a lowering of SHBG, this makes some sense if the goal is to speed the elimination of a substance that the body has an excess of.

 

[daleb]

does testosterone binded to shbg prevent it from aromatizing or make it aromatize more readily?

 

[halfape211]

I have a lot to learn and don't know it all. But I've never seen documentation that didn't consider Free Test or Bioavailable test to be less important than that which has already been bound with albumin or SHBG. After all Bioavailable T is what you body uses. Not trying to argue, just looking to get the facts

 

[Mprtz]

I have a lot to learn and don't know it all. But I've never seen documentation that didn't consider Free Test or Bioavailable test to be less important than that which has already been bound with albumin or SHBG. After all Bioavailable T is what you body uses.

Did you get the wording backwards here for what you wanted to say?

The term "bioavailable" is applied based on certain assumptions. I guess I'm not sure I believe that these assumptions are correct.

 

[halfape211]

Did you get the wording backwards here for what you wanted to say?

The term "bioavailable" is applied based on certain assumptions. I guess I'm not sure I believe that these assumptions are correct.

Oh I probably jumbled my word, yes. From everything I read, Bioavailable T is available for use by the body, because it is not bound to the proteins. The T attached to SHBH is used by the body but it is not as available. But heck, you could be correct. I'm just stating what I have read and what my TRT doc has told me.

 

[Mprtz]

I don't pretend to know definitively either - but I like to think I have good scientific instincts and I get the sense that what medical science believes about bound sex hormones is inconsistent or just wrong.

Let's say we have a guy who has really low SHBG and low total T but his free T is in range (due to low SHBG).

He should feel fine, right? I bet if you find some guys like that and ask them they will not feel fine.

 

[daleb]

I don't pretend to know definitively either - but I like to think I have good scientific instincts and I get the sense that what medical science believes about bound sex hormones is inconsistent or just wrong.

Let's say we have a guy who has really low SHBG and low total T but his free T is in range (due to low SHBG).

He should feel fine, right? I bet if you find some guys like that and ask them they will not feel fine.

That was me. LH and FSH at low 3's. Total T 200, free t about 1/3 into the lab range. Felt like absolute shit.

 

[halfape211]

I don't pretend to know definitively either - but I like to think I have good scientific instincts and I get the sense that what medical science believes about bound sex hormones is inconsistent or just wrong.

Let's say we have a guy who has really low SHBG and low total T but his free T is in range (due to low SHBG).

He should feel fine, right? I bet if you find some guys like that and ask them they will not feel fine.

Your thoughts on SHBG is interesting and I'll throw a little skepticism in, when I read more about SHBG.
I think he said that his Free T was lacking as well as TT. Anyways, On the surface it looks like he needs TRT,

 

[halfape211]

That was me. LH and FSH at low 3's. Total T 200, free t about 1/3 into the lab range. Felt like absolute shit.

Man. that is shitty numbers. I thought I felt crappy at 300

 

[halfwit]

Free testosterone is very important, but you need to have adequate total testosterone to generate the proper responses in other systems as they look for bound (SHBG and albumin bound).

The way I see it is that a healthy total testosterone comes first, then if the person still doesn't feel well, free testosterone should be looked at. Free testosterone is indeed what aromatizes, and like it, free estradiol is what brings on the side effects. There's a formula used to calculate free by using SHBG and total, which I think is woefully inadequate, and LC-MS/MS is the way to go.

Just remember, it's not the numbers that matter so much; it's how you FEEL at those numbers. Some guys feel fine with a total testosterone in the 400's, while some of us feel like absolute crap. Free testosterone is part of that reason, although I suspect that androgen receptors are discounted in their role in this whole shebang.

I still wonder about those guys like newtohrt that have GREAT numbers, but feel like crap because they do have a very low SHBG. Intuitively one would think it's a blessing to have low SHBG, but I suspect it's a balance that's key.

My .02c

 

[IMT staff]

SHBG merely preserves T in the blood stream. Free T is by far he most important.

 

[Graeme]

There was a study done last year which compared symptoms of men with low total (below 300 ng/dL / 10.5 nmol/L) or free (below 6.3 ng/dl / 220 pmol/L) testosterone. The group with low free testosterone had more symptoms than that with low total testosterone.

Free Testosterone Could Be Key to Diagnosing Hypogonadism | ISSM

I posted these links a day or two ago. This paper suggests offering TRT to patients whose total testosterone is less than 350 ng/dL (12 nmol/L), or whose calculated free testosterone is below 8 ng/dL.

http://www.menshealthboston.com/pdf/2011_Testosterone-Deficiency.pdf

And this has a range of opinions from experts, who use similar cut-offs. The calculated free testosterone value they use is around 6.5 ng/dL / 230 nmol/L, so slightly lower than the above.

http://www.menshealthboston.com/pdf...ynthesis-of-International-Expert-Opinions.pdf

I think that it's worth using as a diagnostic tool, but that's probably because my free testosterone tends to sit in the 6.5 to 8 ng/dL / 230 to 250 nmol/L range.

 

[SugarMouth]

Excellent feedback! Thank you for all the great replies!

 

[IMT staff]

There was a study done last year which compared symptoms of men with low total (below 300 ng/dL / 10.5 nmol/L) or free (below 6.3 ng/dl / 220 pmol/L) testosterone. The group with low free testosterone had more symptoms than that with low total testosterone.

Free Testosterone Could Be Key to Diagnosing Hypogonadism | ISSM

I posted these links a day or two ago. This paper suggests offering TRT to patients whose total testosterone is less than 350 ng/dL (12 nmol/L), or whose calculated free testosterone is below 8 ng/dL.

http://www.menshealthboston.com/pdf/2011_Testosterone-Deficiency.pdf

And this has a range of opinions from experts, who use similar cut-offs. The calculated free testosterone value they use is around 6.5 ng/dL / 230 nmol/L, so slightly lower than the above.



http://www.menshealthboston.com/pdf...ynthesis-of-International-Expert-Opinions.pdf

I think that it's worth using as a diagnostic tool, but that's probably because my free testosterone tends to sit in the 6.5 to 8 ng/dL / 230 to 250 nmol/L range.

You wanna do a summary on this for our blog? We will give your handle the credit. Summary cannot be posted anywhere else on line. It can be short and sweet if you would like.

Let me know please.

 

[AJ007]

Correct me if I am wrong but it seems with my blood work if I pinned IM my usable the goes up more but if I pin sub q my free t goes up using the same dosages.... ???

 

[halfape211]

Correct me if I am wrong but it seems with my blood work if I pinned IM my usable the goes up more but if I pin sub q my free t goes up using the same dosages.... ???

Usable and Free T are the same.

 

[AJ007]

Usable and Free T are the same.

Thanks for pointing out the mistake but a correction would be more useful.
Total test comes in higher with IM injections and sub q tips the scales towards free T. This is my experience at least. My Dr keeps me at 30+ on the free and doesn't care about the total T.