FT using TruT vs Dialysis methods

[xqfq]

While the TruT model gives more accurate predictions in the majority of the cases, there are still points where the curve doesn’t match the plotted points.

So while pointing out examples of where men on the forum have ED matching TruT shows the model works for the majority of cases, it seems possible that a given guy could be one of those outlier points, and not just because of lab error. I think it’s because it’s not possible to reduce free T to an equation consisting of SHBG, TT and albumin. But I could be wrong- this is just my guess.

 

[DragonBits]

Arguably it might work for you, though these results could be better than average; I've seen other guys have extremely inconsistent results with this same test.
View attachment 8644
Edit: In fact I would bet money that value of 20.7 is completely wrong. Look at how estradiol doubles along with total testosterone, but this measured free T value triples.

Arguably it might work for you, though these results could be better than average; I've seen other guys have extremely inconsistent results with this same test.
View attachment 8644
Edit: In fact I would bet money that value of 20.7 is completely wrong. Look at how estradiol doubles along with total testosterone, but this measured free T value triples.

I wouldn't be surprised that not everyone gets consistent results, there are a lot of factors that could be present. Reporting errors by the user, not actually the test they think it is, lab error, cross reactivity in the test results, etc.

I have often speculated that one's supplements, vitamin / mineral status, general health, other hormones can causes different results for the same testosterone dose.

And I was always suspect of that 20.7 FT number, it just didn't make sense given everything else, but I checked again and that was what the lab result said.

For a few years I was a quality control chemist, so I am probably more sanguine that most about what can cause lab inconsistencies having seen a few in my own work.

 

[Vman]

Omg your doctor would hate me. Ive found that subjectively I feel my best with total T around 1800 lol. When I was at my most symptomatic of hypogonadism, my total was almost 700. He would of thought that was literally perfect. But my free T was at the bottom of the range on one test, and next time I tested it, it was actually below the bottom of the range. Going by just the total is literally insane.

This is where I wonder how accurate the TruT calculator is.

Before I started TRT my TT was 718 ng/dL and my FT was 72 pg/mL. On 14mg ED test cypionate my TT was 730 ng/dL and my FT was 202 pg/mL and my body composition was drastically different (gained muscle mass, lost fat). I did not change a single thing in my routine (exercise, eating, sleeping, etc.) that I had been doing for over 5 years.

So even if direct FT testing is inaccurate it is still a range of normal people (52-280 pg/mL) and there was definitely a big difference for me from when I was at 72 pg/mL vs. 202 pg/mL.

 

[Gman86]

This is where I wonder how accurate the TruT calculator is.

Before I started TRT my TT was 718 ng/dL and my FT was 72 pg/mL. On 14mg ED test cypionate my TT was 730 ng/dL and my FT was 202 pg/mL and my body composition was drastically different (gained muscle mass, lost fat). I did not change a single thing in my routine (exercise, eating, sleeping, etc.) that I had been doing for over 5 years.

So even if direct FT testing is inaccurate it is still a range of normal people (52-280 pg/mL) and there was definitely a big difference for me from when I was at 72 pg/mL vs. 202 pg/mL.

Very interesting. Do you have your SHBG level for both sets of labs. Without it, this means nothing unfortunately

 

[fifty]

Many labs are a magic 8 ball. Would you trust that your bathroom scale is right if you could only weigh yourself once every 6 weeks and it cost $100 each time?

Where did you get your freeT test? Equilibrium dialysis for freeT is generally hundreds of dollars.

 

[Vman]

Very interesting. Do you have your SHBG level for both sets of labs. Without it, this means nothing unfortunately

I only have my SHBG for the lab on 14mg ED. It was 35. SHBG only affects the TruT calculator a little. The difference betweeen 15 SHBG and 60 SHBG at 730 TT is like 3 FT. So SHBG definitely does not account for the difference in FT.

 

[Gman86]

I only have my SHBG for the lab on 14mg ED. It was 35. SHBG only affects the TruT calculator a little. The difference betweeen 15 SHBG and 60 SHBG at 730 TT is like 3 FT. So SHBG definitely does not account for the difference in FT.

Wow really? So how the hell can this thing be accurate when it’s basically just based off of total T?

 

[DragonBits]

Wow really? So how the hell can this thing be accurate when it’s basically just based off of total T?

It strongly suggest SHBG isn't as significant as we think. Assuming it's right of course.

Most doctors do pay more attention to total T than to anything else.

 

[Vman]

Wow really? So how the hell can this thing be accurate when it’s basically just based off of total T?

I think that's the whole point. TruT has determined that SHBG has a much lower impact on FT than previously thought. I only started TRT because my doc said my FT numbers were really low even though my TT was 718. If I had been going off of just the TruT calculator, I probably would have never started TRT. The real question is what was my FT if I had used ultrafiltration or equilibrium dialysis before I started TRT?

At the end of the day, even if direct FT is off by 47%, it's still a range of real lab results from real people. The highest FT they have found is 280 and the lowest is 52. My FT was 284 on 20mg ED so that's just barely above the highest FT they have found using that test.

 

[madman]

Wow really? So how the hell can this thing be accurate when it’s basically just based off of total T?

Forgive me for being harsh but what is it that you seem to be pig headed too here!

It has been explained numerous times to you and you just keep making brain dead statements!

It is not just based of TT..... it is TT, SHBG, Albumin.....and if you could grasp the reason why at higher TT/SHBG levels that FT levels only decline modestly.....is because as shown in the newer research regarding SHBG:T binding it was discovered that the binding affinities of the two sites (two binding sites on the SHBG dimer) are not identical.

"SHBG dimer exhibits conformational allostery in binding testosterone"

"Recent studies of testosterone binding to SHBG using modern biophysical techniques suggest that SHBG circulates as a homodimer and that there is complex allosteric interaction between the two binding sites on the SHBG dimer, such that the binding affinities of the two sites are not identical (34)"




TruT
*This algorithm is based on experimental data demonstrating that testosterone’s binding to SHBG is a multi-step process involving an allosteric interaction between the two binding sites on the SHBG dimer.








* highlighted in green- refer to the linear law-of-mass-action model/equation Vermueulen (cFTV)

*highlighted in blue- refer to the new Multi-step Dynamic Binding Model with Complex Allostery (TruT calculated)



[0302] The current equations based on homogenous SHBG:T interaction (equal affinity of T for each of the monomers within SHBG dimer and without allostery in SHBG dimers) proposed by Vermeulen and others (13, 17) are based on the assumption that each SHBG dimer binds two testosterone molecules, and that each of the two binding sites on SHBG dimer has similar binding constants (data not shown). It is demonstrated herein that the current model of testosterone binding to SHBG that has formed the basis of the law-of-mass-action equation is erroneous; the free testosterone levels derived from these equations display substantial discrepancy from the values obtained by equilibrium dialysis (18). Based on binding isotherms, ligand depletion experiments, and isothermal titration calorimetry (ITC), we provide experimental evidence of complex allostery between the binding sites on the two SHBG monomers in the presence of the ligand. Based on this new model of testosterone binding to SHBG, described herein is a novel algorithm for the calculation of free testosterone, applied it to samples derived from randomized testosterone trials in men and women, and compared the results with those obtained using equilibrium dialysis.

[0354] Circulating free testosterone (FT) levels have been used widely in the diagnosis and treatment of hypogonadism in men. Due to experimental complexities in FT measurements, the Endocrine Society expert panel has recommended the use of calculated FT (cFT) as an appropriate approach for estimating FT. It is demonstrated herein that the prevailing model of testosterone's binding to SHBG, which assumes that each SHBG dimer binds two testosterone molecules and that the two binding sites on SHBG have similar binding affinity, provides values of free testosterone that differ substantially from those obtained using equilibrium dialysis.

[0359] The current model of testosterone's binding to SHBG assumes that each SHBG dimer binds two testosterone molecules, and that each of the two binding sites on SHBG dimer has similar binding affinity. Equations to determine FT were proposed by Vermeulen and others (Rosner et al 2007, Sodergard et al 1982, Vermeulen et al 1971, Mazer 2009)(Sodergard et al 1982, Vermeulen et al 1971). We show here that the prevailing model of testosterone's binding to SHBG is erroneous. The data from equilibrium dialysis and isothermal titration calorimetry (ITC) experiments provide evidence for ligand modulated allosteric interaction between the binding sites on the two SHBG monomers.

[0368] Various molecular models of testosterone's binding to SHBG were numerically tested using LabVIEW™ (National Instruments, Austin, Tex.) toolkit (Zakharov et al 2012) (available on the world wide web at code.google.com/p/labview-biochemical-framework/). Parameter estimation for the models was performed as described previously (Zakharov et al 2012). Numerical correction for the equilibrium dialysis was incorporated as a part of every simulation model. Since some of the models and equations (Sodergard et al 1982, Vermeulen et al 1999, Nanjee and Wheeler 1985) were developed essentially before the confirmation of the 2 binding sites per SHBG dimer (Avvakumov et al 2001) we adjusted SHBG concentration by the factor of 2 for these models.

[0376] The simplest of the SHBG T interaction models is Vemeulens model, assuming that each binding site interacts with T with the same affinity, regardless of the other binding site occupancy (FIG. 6, model A).

[0387] Relation between Percent FT with Total Testosterone and SHBG. Intra-dimer complex allostery suggests that SHBG can regulate FT fraction over a wide range of total testosterone concentrations without getting saturated. Indeed, it was found that percent FT calculated using the new model changed very modestly over a wide range of total testosterone concentrations. In contrast, the Vermeulen's equation suggests a negative relation between percent FT and total testosterone. Furthermore, as SHBG concentrations increase, percent FT calculated using our new model shows only a modest decline in contrast to the marked decline in percent FT calculated using Vermeulen's equation.




key points being:

*Intra-dimer complex allostery suggests that SHBG can regulate FT fraction over a wide range of total testosterone concentrations without getting saturated.

*Indeed, it was found that percent FT calculated using the new model changed very modestly over a wide range of total testosterone concentrations.

*Furthermore, as SHBG concentrations increase, percent FT calculated using our new model shows only a modest decline in contrast to the marked decline in percent FT calculated using Vermeulen's equation.




Here is the big flaw in the outdated calculated FT methods based off of linear law-of-mass action models:

[0376] The simplest of the SHBG T interaction models is Vemeulens model, assuming that each binding site interacts with T with the same affinity, regardless of the other binding site occupancy (FIG. 6, model A).




Regarding the TruT model/algorithm:

[0390] The new dynamic model leads to the reconsideration of several dogmas related to testosterone's binding to SHBG and has important physiologic and clinical implications. First, the fraction of circulating testosterone which is free is substantially greater (2.9±0.4%) than has been generally assumed (% cFTV 1.5±0.4%). Second, percent FT is not significantly related to total testosterone over a wide range of total testosterone concentrations. However, the percent FT declines as SHBG concentrations increase, although it does not decline as precipitously as predicted by the Vermeulen's model. Due to the allostery between the two binding sites, SHBG is able to regulate FT levels in much larger dynamic range.

 

[madman]

Reappraisal of Testosterone’s Binding in Circulation: Physiological and Clinical Implications




A recent reappraisal of testosterone binding to SHBG using modern biophysical techniques indicated that the two binding sites on the SHBG dimer are not equivalent and that there is an allosteric interaction between the binding sites on the SHBG dimer such that the second testosterone molecule binds SHBG with a substantially different affinity than the first binding site (34).




*SUBSTANTIALLY DIFFERENT AFFINITY

 

[Cataceous]

Since I have a fair number of measurements, I'll just put this out:

Not great correlation. The outliers are tending to occur at higher or lower SHBG.

What's giving me more confidence in Tru-T is that with it I get almost perfect linearity between testosterone dose and free testosterone, a relationship I believed should exist:

Now see what happens when I try this with direct free T:

 

[xqfq]

Interesting. As an additional data point, here's some plots for me over the past year:

(I'm not sure how to make my graphs as fancy as yours)

 

[ncsugrad]

Interesting. I wonder what sort of “normal” ranges we should expect using truT? Are they the same? My results are similar in that truT is about 2x higher than the measurements I have from labcorp. I was already slightly over normal using labcorp measurements but using truT with the same ranges I’m quite high. But I don’t know that we should be using the same ranges.

I don’t know. It’s all confusing to me how results can be they different and still be used for medical decisions.

 

[Cataceous]

... I wonder what sort of “normal” ranges we should expect using truT? ...

Quoting research provided by madman: "Based on the new data on the distribution of free testosterone levels in healthy men the target range of free testosterone has been determined to be 164 to 314 pg/ml". That is, about 16-31 ng/dL. The values may not directly equal the values of other methods, but ideally they would be correlated, meaning you multiply results of one method by a constant to obtain the values a different method would produce. This correlation should exist between free T calculated by Tru-T and free T measured by either equilibrium dialysis or ultrafiltration. Correlation with the older Vermeulen free T calculation is less good, and it's even worse with the inexpensive direct free T lab test.

 

[Deleted member 12831]

Not only does it seem odd that with a TT 837 ng/dL and an SHBG on the higher end 52 nmol/L that your FT is only 8.4 ng/dL (reference range 5.2-28.0 ng/dL) which is closer to the bottom end.....it would be hard to believe that anyone at such FT level would feel well let alone pretty good.....and you stated that....."Still this FT testings and results are confusing and I agree it matters more how you feel then the lab result numbers. I think I can raise my TT and FT and feel a little better. But I do feel pretty good now"

Now if we want to try and compare as you have done......again keeping in mind that the main issue is the reference ranges between testing methods from the various labs for FT by Equilibrium Dialysis or Ultrafiltration are different and not on the same scale as TruT.....so until reference ranges are standardized and there are harmonized reference ranges for Free Testosterone as have been previously done for Total Testosterone (CDC and its Hormone Assay Standardization program) than doubtful you could do an accurate comparison.

Here is some of the labs posted by members that had FT tested using ED or Ultrafiltration:

Below is the members lab results testing his FT at Labcorp using.....Testosterone, F EQLIB + T LC/MS (Final).

As you can see his TT is 1004 ng/dL, SHBG 60.1 nmol/L (high) and Albumin 4.6 g/dL and his FT 18.47 ng/dL (reference range 5.00-21.00 ng/dL).....so even with a high SHBG of 60.1 nmol/L his FT is close to the top end of the reference range.

Your TT 837 ng/dL which is not an extreme difference compared to his TT 1004 ng/dL, your SHBG 52 nmol/L is a little lower than his 60.1 nmol/L, and your Albumin 4.2 g/dL is slightly lower than his 4.6 nmol/L.....your FT is 8.4 ng/dL (close to the bottom end of the reference range) and his FT is 18.47 ng/dL (close to the top end of the reference range).

Seems odd to have such a significant difference in FT levels when not only is his TT not significantly higher than yours but his SHBG is higher and Albumin is only slightly higher.
View attachment 8643




Now if we take those numbers and use the TruT calculated method.....albeit the reference ranges are on a different scale.
.

TT 1004ng/dL, SHBG 60.1 nmol/L, Albumin 4.6 ng/dL than his FT is 30.73 ng/dL (reference range 16-31 ng/dL).....so his FT is right at the top end of the reference range.
View attachment 8639
Now again as you can see when he tested FT using Equilibrium Dialysis his FT 18.47 ng/dL (reference range 5.00-21.00 ng/dL).....is close to the top end of the reference range.




Here is another members lab results testing his FT at Quest Labs using.....Testosterone, FR (DIALYSIS) AND TOTAL (LC/MS/MS).

The Quest Labs reference range for FT and the units are 35.0-155.0 pg/mL.....different from the previous members Labcorp reference range/units 5.00-21.00 ng/dL.

As you can see his TT is very high 1627 ng/dL, SHBG 47 nmol/L and Albumin 4.8 g/dL and his FT is very high 303.3 pg/mL (reference range 35.0-155.0 pg/mL).....so even with a highish SHBG of 47 nmol/L his FT is almost double the top end of the reference range.
View attachment 8641
View attachment 8640



Now if we take those numbers and use the TruT calculated method.....albeit the reference ranges are on a different scale.


TT 1627 ng/dL, SHBG 47 nmol/L, Albumin 4.8 ng/dL than his FT is 52.75 ng/dL (reference range 16-31 ng/dL).....so his FT is over more than 3/4 the top end of the reference range.

TruT reference range is 16.4-31.6 ng/dL or 164-316 pg/mL.....so if we take his FT 52.75 ng/dL and covert to pg/mL it would be roughly 528 pg/mL.....so his FT is over 3/4 the top end of the reference range.
View attachment 8642Now again as you can see when he tested FT using Equilibrium Dialysis his FT is 303.3 pg/mL (reference range 35.0-155.0 pg/mL).....is almost double the top end of the reference range.



Another members results tested using Equilibrium Dialysis, Vermuelen and TruT calculated.....unfortunately he did not post up labs.....which is needed!
View attachment 8645


Below is another members lab results testing his FT at Labcorp using.....Testosterone, F EQLIB + T LC/MS (Final).



He has posted numerous labs stating he normally has high SHBG in the 60-70 nmol/L range.

These are his labs from 4/2019.

As you can see his TT is 972 ng/dL, SHBG was not tested? but from other labs posted he usually runs high 60-70 nmol/L and Albumin 4.3 g/dL (mean) and his FT 30.62 ng/dL (reference range 5.00-21.00 ng/dL).....so even with a high SHBG 60-70 nmol/L his FT is over 3/4 the top end of the reference range.
View attachment 8648




Now if we take those numbers and use the TruT calculated method.....albeit the reference ranges are on a different scale.

Mind you we do not have know his SHBG but will use the higher end number of 70 nmol/L as he usually has SHBG in the 60-70 nmol/L range.

TT 972 ng/dL, SHBG 70 nmol/L, Albumin 4.3 ng/dL (mean) than his FT is 30.25 ng/dL (reference range 16-31 ng/dL).....so even with a high SHBG of 70 nmol/L his FT is almost top end of the reference range.
View attachment 8647
Now again as you can see when he tested FT using Equilibrium Dialysis his FT 30.62 ng/dL (reference range 5.00-21.00 ng/dL).....is over 3/4 the top end of the reference range.

Again we have no idea what his SHBG level was when he had lab work done but he is very well know to have high SHBG as he has stated many times let alone show in lab work he has posted previously.

I think this is part of the issue I have with this. Ng/dl is a unit of measurement . Different labs would have a different range because of variations in populations tested. We may have a total testosterone top of the range variation of 726 to 1,130 ng/dL. But that does not mean one lab at 726 ng/dl means the same as the other with the top of the lab range at 1100 ng/dl. ng/dl is just a unit of measurement. 700 ng/dl in one lab means the same as 700ng/dl in another.

 

[Cataceous]

... 700 ng/dl in one lab means the same as 700ng/dl in another.

Historically this has not been the case. Different methods and assays can produce quite different results even from the same samples; the differences are not just from differing control populations. Fortunately there is significant work on harmonization underway, such that labs will internally adjust their results to be more comparable on some "universal" scale.

 

[Deleted member 12831]

It strongly suggest SHBG isn't as significant as we think. Assuming it's right of course.

Most doctors do pay more attention to total T than to anything else.

You are right