AGE SPECIFIC CALCULATED FREE TESTOSTERONE RANGES IN ADULT MEN

[Jerajera]

No, a cFTV (calculated free testosterone by Vermeulen) of 17.2 ng/dL is above average for healthy young men. Average for them is around 15 ng/dL. Or at least it was some decades back.

As I said above:

If you use the Vermeulen calculation then you can compare yourself to a range for healthy young men of about 70-230 pg/mL (7-23 ng/dL).​

@Cataceous, are those ranges for what is considered normal in general 2 standard deviations on each side of the mean? Meaning 23ng/dL would be approximately the 98th percentile?

 

[Cataceous]

@Cataceous, are those ranges for what is considered normal in general 2 standard deviations on each side of the mean? Meaning 23ng/dL would be approximately the 98th percentile?

Yes. Here is one such study:

https://journals.sagepub.com/doi/pdf/10.1258/000456306778520115

 

[madman]

Wow! You’re good. I should be sending you my copayment! Currently inject once per week, 130-140 mg. This was at the trough.

You are hitting a cFTV 17.2 ng/dL at the true trough (7 days post-injection).

Keep in mind as of now cFTV tends to overestimate slightly when compared against a state of the art/standardized ED assay.

Even then you would most likely still be hitting a trough FT 15 ng/dL (7 days post-injection).

Now think about how much higher your peak TT/FT (8-12 hrs post-injection) during the first 2-3 days every week would be!




The testing method used for FT was state-of-the-art direct ED method (ED LC-MS/MS)!

What percentile of healthy young men would even be hitting a peak not trough FT 17.1 ng/dL!

Age-stratified reference ranges for directly measured (ED LC-MS/MS) serum free testosterone in healthy men

www.excelmale.com

We present 95% mFT age-stratified reference ranges

Age category (years)	Median mFT (ng/dl)	95% mFT reference range (ng/dl)
18-29 (n=140) 30-39 (n=252)	12.0 9.8	6.7-25.3 4.9-18.5
40-49 (n=207)	8.1	4.3.14.2
50-59 (n=146)	7.1	3.8-12.8
60-69 (n=126)	6.4	3.4-11.7
70-79 (n=125)	5.6	2.7-8.7

*The gold-standard for the determination of FT levels is considered to be directly measured free testosterone (mFT) using equilibrium dialysis followed by mass spectrometry (ED LC-MS/MS). However, no widely accepted reference ranges are available for this clinical parameter. We established mFT reference ranges for healthy men aged 18 to 69 years


*Serum samples were analyzed from healthy men participating in the SIBLOS/SIBEX and EMAS studies, both population-based cohort studies


* mFT levels were measured in 867 men using ED LC-MS/MS as previously reported (1).


Reference: 1. Fiers T, Wu F, Moghetti P, Vanderschueren D, Lapauw B, Kaufman JM. Reassessing Free-Testosterone Calculation by Liquid Chromatography–Tandem Mass Spectrometry Direct Equilibrium Dialysis. J Clin Endocrinol Metab. 2018;103(6). doi:10.1210/jc.2017-02360

Reassessing Free-Testosterone Calculation by Liquid Chromatography–Tandem Mass Spectrometry Direct Equilibrium Dialysis

Reassessment of FT in women and men with state-of-the-art methodology confirms previously established FT percentages but highlights limitations of differen

academic.oup.com

In the current study, we used a state-of-the-art direct ED method to reassess FT in sets of representative serum samples. This method takes advantage of the ability of a highly sensitive and accurate measurement of T by liquid chromatography–tandem mass spectrometry (LC-MS/MS) to reliably measure the low FT concentration directly in the dialysate after ED. This more straightforward method avoids potential sources of inaccuracy in indirect ED, such as those resulting from tracer impurities or from measures to limit their impact (e.g., sample dilution). We then used the measured FT results to re-evaluate some characteristics of two more established and a more recently proposed calculations for estimation of FT.

 

[madman]

Factors associated with variations in calculated free testosterone in men

OBJECTIVE Sociodemographic, lifestyle and medical variables influence total testosterone (T) and sex hormone-binding globulin (SHBG) concentrations. The relationship between these factors and “free” T remains unclear. We examined 21 sociodemographic, lifestyle and medical predictors influencing...

www.excelmale.com

 

[madman]

Even then we need to wait on harmonized FT reference ranges based on a standardized FT assay (ED-LC/MS/MS).

Similar to what was done for harmonized TT.

*Assays that are standardized are designed to provide accurate results, traceable to “true” value-assigned certified reference materials and gold-standard reference methods.

The CDC has been working hard on this and it is not too far off now!

Soon enough we will have a CDC Hormone Standardization Program (CDC HoSt) Certified Free Testosterone Procedure and a harmonized reference range for free testosterone!

CDC’s Clinical Standardization Programs (CDC CSP): Ensuring the Accuracy and Reliability of Chronic Disease Biomarker Tests

www.excelmale.com

View attachment 43656




Something to keep in mind when it comes to using/relying upon the calculated FT methods!

*Currently, the CDC is developing a harmonized method for free T based on calculated free T using REVISED FORMULAE. This may bring the measurement of free T to a referable standard in clinical laboratories and common reference intervals that all clinicians can use

How to co relate RIA and equilibrium dialysis reports

www.excelmale.com

Take home points:

*Assays that are standardized are designed to provide accurate results, traceable to “true” value-assigned certified reference materials and gold-standard reference methods. Results obtained using standardized methods can be compared across assays, institutions, populations, and past and future test results, thereby improving diagnosis, treatment, and outcomes of patients

* Limitations of using free testosterone by equilibrium dialysis and calculated free testosterone concentrations in practice are the lack of assay standardization, an accuracy-based quality control program, and a harmonized reference range. Until these limitations are addressed, free testosterone by equilibrium dialysis and calculated free testosterone should use reference ranges established by individual laboratories or their specific assay method

Key points here!

* While the use of cFT may be of value in preventing misdiagnosis and overtreatment of hypogonadism, it has its limitations. Therefore, reassessing cFT calculators to enhance their accuracy and alignment with equilibrium dialysis measurement of free T is needed. Additionally, standardizing and validating cFT calculators, as well as optimizing available assays for total T and SHBG are crucial steps.




Again something to keep in mind when it comes to using/relying upon the calculated FT methods!

*Currently, the CDC is developing a harmonized method for free T based on calculated free T using REVISED FORMULAE. This may bring the measurement of free T to a referable standard in clinical laboratories and common reference intervals that all clinicians can use

Use of calculated FT in men: advantages and limitations

https://journals.lww.com/co-endocrinology/abstract/2024/12000/use_of_calculated_free_testosterone_in_men_.7.aspx INTRODUCTION Clinical practice guidelines on the diagnosis of male hypogonadism focus on clinical signs and symptoms of androgen deficiency, as well as biochemical assessment of...

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WHAT ARE THE LIMITATIONS OF CALCULATED FREE TESTOSTERONE?

Although free T, if accurately measured, may be physiologically and clinically relevant, the complexity of directly measuring free T limits its introduction into routine clinical practice. Alternatively, clinicians rely on cFT as an acceptable estimate, and thus proxy,of free T concentrations. Existing calculators, including models by Vermeulen, Ly-Handelsman and Zakharov, use calculation methodologies based on total T and SHBG concentrations [3&&]. Free T calculator performance was investigated by comparing cFT values using these three different calculators against measured free T values obtained through the gold standard LC/MS-MS coupled with equilibrium dialysis. The Vermeulen formula appeared to perform best across a wide range of SHBG levels, whereas the Ly-Handelsman model showed significant divergence from measured free T at lower SHBG levels [9]. However, the Vermeulen formula exhibits suboptimal accuracy and tends to overestimate measured free T by 20–30%. Despite this, the current model remains a widely accepted tool for free T calculation due to its ability to integrate a broad range of SHBG, total T and albumin concentrations. This advantage is particularly important in conditions where SHBG concentrations are impacted and/or when total T concentrations are in the borderline range of the lower limit of normal [9].

The use of free T calculators in clinical routine is, however, hindered by a number of imperfections of which clinicians should be aware of when interpreting cFT values (Table 2). Firstly, quality of cFT results depends on the performance of assays used to measure total T, SHBG and albumin. For instance, automated SHBG immunoassays lack standardization[24]. Furthermore, these models are simplified representations of the true binding milieu and may not account for all variables influencing the equilibrium between total and free T, such as SHBG-binding affinity variability and stoichiometry [3&&].

This could particularly be important in men with SHBG polymorphisms. These genetic variations can potentially influence binding affinity between T and SHBG, which is not taken into account in calculators that use a constant binding affinity. In a recent study focusing on the impact of relatively common SHBG single nucleotide polymorphisms (allelic prevalence between 0.5 and 58.2%), healthy men who were heterozygotes for rs6258 had lower serum SHBG levels, while those who were heterozygotes for rs6259, homozygotes for rs727428 and carriers of rs1799941 had higher serum SHBG levels compared to healthy men with wild-type SHBG. These SHBG polymorphisms influenced both SHBG and total T levels, with total T being higher in rs727428 homozygotes and in carriers of rs5934505, rs1799941 and rs6259. Interestingly, these variants did not influence cFT or measured free T concentrations [25&&].

As cFT is a calculated variable, its validity is debated and limited by a lack of standardization and quality control resulting in variable reference ranges. The Vermeulen model, for instance, overestimates free T by 20–30%. Moreover, there is no consensus on a universal cut-off between low and normal cFT values. A thorough review detailing the pitfalls of various methodologies for total and free T assessment was recently published [3&&].

There is a need to enhance the measurement of free T, as cFT values are only approximations. There is also a pressing requirement to reassess current freeT calculators to improve their accuracy and alignment with direct measurement methods. Moreover, additional research is necessary to optimize existing commercially available assays for SHBG, as well as studying SHBG-binding affinity in specific patient groups (e.g. obesity and diabetic individuals) to accurately reflect the true binding environment. Standardizing and validating cFT calculators is also crucial to establish harmonized reference ranges and achieve consensus on cutoff values between low and normal cFT levels. Promising recent developments include the establishment of age-stratified reference ranges for free T in healthy nonobese adult men using the gold standard equilibrium dialysis coupled to LC-MS/MS, showing the expected age-related decline in serum-free T concentrations [26,27]. These efforts represent a significant step towards improving the accuracy of free T measurements and calculations in clinical practice.