kikero:
How can my freeT is in the middle of the range for 20-50yr old men (8pg/ml to 54pg/ml) when my Total T is in the very low of the normal range ? And by the way 24pg/ml is 2,4ng/dl which is considered very low in other countries? Moreover, Tru-T calculator gives back freeT of around 8ng/dl. Still low. My FSH and LH shows that my HPTA seems to “accept” my eventual lowT just fine. They´ve been higher before (around 4 or 5) with no materialy relevant change to Total T or freeT.
If you really want to understand this you’ll have to dig into this thread and really spend some time with especially the last few posts I did there. It is quite arcane but very liberating once you understand the state of things and the fact we don’t know really what the correct reference range for free T is until the CDC standardizes it like they have done for TT and E2. I went into the goriest detail I could possibly go to explain the issues.
Thread:
The number they typically mention in a good Free T level is 30 and above.
My Free Test is 529 pmol/L.
Is it ng/dL or ng/mL or other variations of ng or pg/mLthat I see and typically referenced? LOL
Component
Your Value
Standard Range
Flag
Testosterone Free Calculated
529 pmol/L
163 - 473 pmol/L
H
SHBG
24 nmol/L
21 - 77 nmol/L
Testosterone Total
20.7 nmol/L
6.7 - 25.7 nmol/L
Select posts:
For those interested in summary of all this fT mess…
See the link above. Direct RIA free T method will be 6-7x lower than ED. But some started thinking the units are wrong with labcorp hence they tried to change the pg/ml to ng/dl and say labcorp was using wrong units.
So direct methid correlates well with ED fT but quick check of %fT shows direct fT method way off accuracy wise.
Post in thread ‘Response from LabCorp About Their Incorrect Unit Usages For Their Free Testosterone - Direct - Test’ Response from LabCorp About Their Incorrect Unit …
Go back up to this post and read the links:
Pay attention to units and example for all the fT options.
Also this plot i did:
[image]
Even the “gold standard” equilibrium dialysis assays for fT havent been standardized across US reference laboratories yet. CDC is working on it. Examples above show that calculated fT by Veremulen method typically a decent estimate. Direct RIA free T method correlates with true fT but it is a factor typically 6-7 off once you keep track of units. Most …
Ok I went back and pieced this together:
As I shared above, Labcorp direct FT test is correlated but not absolute measure of fT. Quest dialysis fT test is.
Maybe a picture will help:
[image]
Note the slope of the line on the left panel of the figure. Note that slope (approx 0.15) is very different than the slope of the right panel (~1.2).
This confusion is from folks not being clear about units. The 20 and 30-50 numbers referenced are for an equilibrium dialysis FT measurement in ng/d…
My pleasure and hope it does clear some of this up for those interested.
Absolutely and perceptive observation. You are right, I wasn’t going to get into a pissing match with @disciplined_trt about 5-28 ng/dl vs 9-25 ng/dl. The context of our discussion was about going much higher above a reasonable physiologic reference range and not about the cutoff for the lower part of the range. I know it is shocking but even I have my limits for trying to not be an ass and for the most part I try to e…
And yes I completely agree here. Here is the same plot above except with linear range:
[image]
Yes I understand why good advice is to use each labs free T result only in context of the method’s reported reference range. But if you are selling an expensive assay that claims to be an absolute measure of free Testosterone then you would hope the US reference laboratories would have better agreement than this on the upper reference range.
This type of harmonization process was recently compl…
For those interested in summary of all this fT mess…
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