T Nation

Accuracy of Calculated Free Testosterone Formula in Men

Ill start:

Equilibrium Dialysis measured Free T: 5.3 ng/dl
Tru-T calculated Free T: 11.63 ng/dl.

SHBG 30, Albumin 4.6, Total 382

I’ve tested it, it’s 49. Just curious because if my FT was really 46…with a SHBG of 26, my E2 would likely be higher than 49… Right?

Just thinking out loud that Tru-t is not accurate

Side note - are you on TRT or considering it @grinnin? Sorry if that was already mentioned, but your numbers are low. How do you feel?

The idea of the Tru T calculator is intriguing, yet I am sceptical as it is almost a mystery what exactly the calculator does (patent) and there is nowhere a study to be found that compares measured vs calculated.

I had mine measured preTRT and fT was 6.1 ng/dL.
Tru T gives me 9.1 ng/dL and fT calculated using the Vermeulen equation gives me 5.9 ng/dL.

http://www.issam.ch/freetesto.htm

There is also a freeT, freeDHT and freeE2 calculator using a more complex model available which can be downloaded (simple Excel spreadsheet). I linked it some time ago.

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I am on TRT, those numbers were pre-TRT… Only 3 weeks in and honestly feel much worse since starting. Hopefully it is because my levels are still fluctuating. Just wish my libido would come back. It was much higher when my levels were 382 lol.

please post your results here

Post Your Results: Tru-T Calculated Free T vs Equilibrium Dialysis Free T

I am trying to determine if there is a large discrepancy between measured and calculated Free T. Specifically Equilibrium Dialysis measured Free T… If so I am wondering if many think their Free T is higher than it actually is… Possibly contributing to little symptom relief. I am very research oriented, and stuff like this peaks my curiosity.

You’re confusing the matter, I’m pretty sure the reference ranges are not the same between these two tests. The directly measured Equilibrium Dialysis and the calculated method cannot be compared directly 1:1.

You’re making the assumption these two different tests are using the same reference ranges, I can assure you they are not.

What is your protocol?

When I first started, my doc didn’t test much. My TT averaged 250ish. I took 100mg e3d for 8 weeks and that brought me to around 460ish.

Old doc sold the practice, I stayed and the new doc and he upped me to 60mg e3d. I had problems with e3d, so I went to 34mg EOD and started feeling better. I slowly increased my dose myself until I was at 40mg EOD and stayed there for a while. Found out I had problems with my thyroid and have been working on that this year.

Fast forward - 2 years in, I’m now at 22mg ED, 2.5 grains of Armour Thyroid a day and I really feel good. Libido is lurking but not crazy. Boners are there when I need them… And I generally feel good.

Stay there course. This really is a marathon, not a sprint. If imagine you will have a few bumps in the road, but stick with it and be patient.

Tru-T doesn’t post a reference range. I thought when reviewing values it was important to see the reference range to?

I am speaking in absence of reference ranges… ng/dl is ng/dl the same way a liter of soda is the same as a liter of water. Same volume… picograms per mililiter can be converted to nano grams per deciliter so long as the reference ranges are switched. For example one can not use 5 ng/dl on a reference range of 46-226pg/ml but they could however use labcorps reference range of 9-27 ng/dl…

The reference range is 16-31 ng/dL.

Which would effectively be the same as saying… 160-310 pg/ml, correct? If one wanted to convert to pg/ml they could use Quests reference range of 46-226 pg/ml to compare it to. IE: My free T is 53 Pg/ml which is the same thing as 5.3 ng/dl. If i converted to ng/dl and wanted to compare ng/dl values I would have to compare it to a reference range that was based on nano grams per deciliter. Such as lab corp or Tru-Ts reference range

If the average person had to drink 1 gallon of water per day to be in a healthy range. wouldn’t that be the same as saying 128 fl oz… Units can be converted but reference ranges will have to be switched to match those units.

I could be way off here, but that is how we learn and grow by questioning and obtaining knowledge.

Not when it comes to laboratory testing, it’s too complicated for me to be able to explain. There’s a reason why doctors ignore FT measurements and fixate on the TT number.

The Endocrine Society position

Current methods for measuring free testosterone (fT) are technically challenging and not accurate. The widely used direct immunoassay and tracer analog techniques for measuring fT have been shown to be inaccurate. Equilibrium dialysis, the reference method against which other methods are compared, is labor-intensive and cumbersome, and therefore has had limited clinical adoption.

Recently, Endocrine Society’s Expert Panel acknowledged the experimental problems in fT measurements and concluded that “…the calculation of free testosterone is the most useful estimate of free testosterone in plasma…” For this reason they advocate for indirect “calculator” based methods, where free testosterone can be computed from the total testosterone, SHBG, and albumin concentrations.

Don’t you love how doctors are ignoring the number that matters the most? We really need to revolutionize modern medicine in respect to testosterone replacement therapy. Doctors who prescribe TRT should be more versed on the matter before subjecting their patients to something that they know little about… Seeing some protocols docs prescribe makes me wonder why they have a medical license.

The Tru T calculator gives a very high free T number for me too, for whatever that is worth. Something like 50% over measured. Which is right? I have no idea.

I read that part on Tru-T webiste. “Direct immunoassay and tracer analog techniques for measuring fT have been shown to be inaccurate”. Equilibrium dialysis on the other hand has limited research and is labor intensive… that is why I found the study interesting because Equilibrium Dialysis was researched to be more accurate when compared to 2000+ men and 5 calculators. ED could be the gold standard and due to it being expensive/labor intensive most would rather calculate.

So far me and one other have noticed the same as you. The study I linked says calculators widely over estimate when compared to Equlibrium dialysis… Im pushing for research here and correlation within our community. If free T is being over estimated many men might have lower Free T levels than they think…

Please post your results in my other thread

I only have free T direct measurements, not ED

I see… oh well. Im going to read through the forums to see what I can find on numbers.

If I plug in 2000 total T and 90 for SHBG I get 64 for free T on the truT site. Mine actually came back at 39 but it was the direct method, not ED

The total T test maxed at 1500 so I’m guessing at the 2000 number… it could be lower (I wouldn’t really expect it to be any higher)