What’s wrong with testosterone reference ranges?

[Alexanders]

Free & Bioavailable Testosterone Calculator

This free & bioavailable testosterone calculator estimates these specific testosterone concentrations based on the Vermeulen formulas.

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Looking at the chart for 20-30 years old. The reference range for bioavaible T is 83-257ng/dL, for free T it’s 5.25-20.7ng/dL. Translated that means a man in his twenties with a total testosterone of only 187 ng/dL (6.5 nmol/L) and 30 nmol/L SHBG is still within reference for bioavaible T (87ng/dL) however for free T he’s below reference (3.7ng/dL).

Let’s take another example, total T 778 ng/dL (27 nmol/L) 30 nmol/L SHBG gives 18ng/dL free T, which is within reference at the higher end for free T, but gives 438 ng/dL bioavaible T which is way above reference. If we increase albumin from 4.3 to 4.6 g/dL, free T decrease to 17ng/dL and bioavaible increase to 448ng/dL.

”Abnormally increased testosterone values may be caused by testicular or adrenal tumors or androgen abuse when levels exceed the upper limit of normal by more than 50%.”

For bioavaible T 448 ng/dL exceed the upper limit of normal by more than 50%, for free T 17ng/dL is only in the higher end of the median.

1. Why doesn’t free and bioavaible T correlate?
2. Why is the reference range, especially for bioavaible T, so low?

 

[Matestube]

Why is the reference range, especially for bioavaible T, so low?

How is it low ?
It's a portion of T that remains available outside of the T that's captured by albumin.

I think you mistook it for the range of total T that's usually 200-900.

 

[Ippodrom47]

Last year my (male, 31 y.o. then) Testosterone was 5.550 ng/ml (range 2.49 - 8.36)
Free T 11.74 pg/ml (range 4.50 - 42.00)

My endo said it should be higher as men must have the highest T levels in their mid-30s. However, she also told me not to believe the Free T result too much as many labs screw up the testing process and produce incorrect results. Total Testosterone is determined much easier and thus more accurately.

 

[Alexanders]

How is it low ?
It's a portion of T that remains available outside of the T that's captured by albumin.

I think you mistook it for the range of total T that's usually 200-900.

What’s considered ”normal” is very low testosterone. Free and bioavaible T, nor free androgen index (FAI) correlare with eachother with the ranges above.

I made a new, what I believe to be a more accurate and healthy, reference range for men in their twenties:
Free T: 10-35ng/dL (0.35-1.2 nmol/L)
Bioavaible T: 250-870ng/dL (8.7-30nmol/L)

 

[Matestube]

What’s considered ”normal” is very low testosterone. Free and bioavaible T, nor free androgen index (FAI) correlare with eachother with the ranges above.

I made a new, what I believe to be a more accurate and healthy, reference range for men in their twenties:
Free T: 10-35ng/dL (0.35-1.2 nmol/L)
Bioavaible T: 250-870ng/dL (8.7-30nmol/L)

You're still mistaking bioavailable T and total T ...

 

[Alexanders]

You're still mistaking bioavailable T and total T ...

I don’t think so, bioavaible T is free T + T bound to albumin. Total T is free T + T bound to albumin and SHBG. Since what’s normal for total T depends on SHBG, I didn’t made a reference for neither TT nor SHBG. However I guess 14-40nmol/L TT and 15-50 SHBG could be considered ”normal”.

For FAI the normal ranges should be 50-150. However what’s healthy or optimal depends on the individual, in the lower range there’s risk for hypogonadal symptoms. LH and FSH should always be measured too.

 

[Matestube]

I don’t think so, bioavaible T is free T + T bound to albumin. Total T is free T + T bound to albumin and SHBG. Since what’s normal for total T depends on SHBG, I didn’t made a reference for neither TT nor SHBG. However I guess 14-40nmol/L TT and 15-50 SHBG could be considered ”normal”.

For FAI the normal ranges should be 50-150. However what’s healthy or optimal depends on the individual, in the lower range there’s risk for hypogonadal symptoms. LH and FSH should always be measured too.

Ranges are off by a few folds, not by a few percent like you seem to imply.

A healthy total T is around 2200 ng/dl around the clock, not 800 measured at peak of the morning.