Please see results below for a 19yo.
The free t surprised me cuz it's high normal. But the total t is low. I gather he has a low shbg which they didn't test.
Would you treat this for low t despite having a great free t?
Testosterone, Free, S
Normal Range: 5.36 -
21.2 ng/dL
17.8 result
Testosterone, Total by
Mass Spectrometry,
Serum
Normal Range: 240
950 ng/dL
386 result
Would you treat this for low t despite having a great free t?
If the FT result is accurate not a chance!
Although TT is important to know FT is what truly matters as it is the active unbound fraction of T responsible for the positive effects!
Having a low/normal or low FT with signs and symptoms of testosterone deficiency would merit treatment.
Keep in mind it is critical to use the most accurate assays when testing TT/FT/BAT.
BAT is not commonly used/relied upon as FT is what truly matters.
The most accurate assays for TT (LC/MS-MS) and FT (Equilibrium Dialysis or Ultrafiltration next best) would be the assays which need to be used.
The only way to know where FT truly sits is to have it tested using the most accurate methods/assays (ED/UF) especially in cases of altered SHBG.
If you do not have access to such then use would need to use/rely upon the go to calculated linear law-of-mass action cFTV which will give a good approx. but keep in mind it tends to slightly underestimate FT.
As I have stated numerous times on the forum you always have the option of using/relying upon calculated FT which would be the linear law-of-mass action cFTV as it has already been validated twice (1st time was done using TT/SHBG assays no longer available) and was then eventually re-validated using current state-of-the-art ED method (higher order reference method) let alone more recently against CDCs standardized Equilibrium Dialysis assay.
Yes it tends to overestimate slightly but it is nothing to fret over!
*Calculated free T using high-quality T and SHBG assays has been considered the most useful for clinical purposes [99]. All algorithms suffer from some inaccuracies, including the variable quality of SHBG IAs [100], not replicating the non-linear nature of T-SHBG binding, different and inaccurate association constants for SHBG and albumin binding [101], and variable agreement with equilibrium dialysis results [99,100]. However, until further developments in the field materialize, the linear model algorithms [in particular, the most used Vermeulen equation [102]] appear to give, despite a small systematic positive bias, acceptable data for the clinical management and research[37,103].
Shit kicker here is with a not so robust TT 386 ng/dL ones SHBG would be low and Albumin would most likely be lower than 4.3 g/dL(default) if FT was healthy/higher-end reference range!
Even then I can already tell you that the FT result you posted was tested using the gold standard Equilibrium Dialysis at Mayo Clinic Laboratories just from looking at the reference range your posted.
So if such is the case then the FT result would be accurate.
Is there always a chance of lab error even when using the most accurate assays.....sure.
If you are in doubt you could always repeat the test to rule this out!
Also something that needs to be kept in mind when testing TT/FT:
* Testosterone levels can fluctuate substantially between different days and sometimes even more rapidly. Assessment of androgen status should be based on more than a single measurement.
Again if the results are accurate then the FT is sitting at the high-end of the reference range and the patients FT level would be healthy!
Regarding polymorphism of the AR/CAG repeat lengths (long/short) would not get too caught up on this as it is not part of routine testing let alone the testing is not commonly available to the general public and even then there is much more research that needs to be done before this is even implemented!
Reference Values
TESTOSTERONE, TOTAL
Males
0-5 months: 75-400 ng/dL
6 months-9 years: <7-20 ng/dL
10-11 years: <7-130 ng/dL
12-13 years: <7-800 ng/dL
14 years: <7-1,200 ng/dL
15-16 years: 100-1,200 ng/dL
17-18 years: 300-1,200 ng/dL
≥19 years: 240-950 ng/dL
Tanner Stages*
I (prepubertal): <7-20
II: 8-66
III: 26-800
IV: 85-1,200
V (young adult): 300-950
TESTOSTERONE, FREE
Males (children):
<1 year: Term infants
1-15 days: 0.20-3.10 ng/dL*
16 days-1 year: Values decrease gradually from newborn (0.20-3.10 ng/dL) to prepubertal levels
*Forest MG, Cathiard AM, Bertrand JA. Total and unbound testosterone levels in the newborn and in normal and hypogonadal children: use of a sensitive radioimmunoassay for testosterone. J Clin Endocrinol Metab. 1973;36(6):1132-1142
1-8 years: <0.13 ng/dL
9 years: <0.13-0.45 ng/dL
10 years: <0.13-1.26 ng/dL
11 years: <0.13-5.52 ng/dL
12 years: <0.13-9.28 ng/dL
13 years: <0.13-12.6 ng/dL
14 years: 0.48-15.3 ng/dL
15 years: 1.62-17.7 ng/dL
16 years: 2.93-19.5 ng/dL
17 years: 4.28-20.9 ng/dL
18 years: 5.40-21.8 ng/dL
19 years: 5.36-21.2 ng/dL
Method Description
Total Testosterone:
Deuterated stable isotope (d3-testosterone) is added to a serum sample as internal standard. Protein is precipitated from the mixture.
The testosterone and internal standard are extracted from the resulting supernatant by an on-line extraction utilizing high-throughput liquid chromatography. This is followed by conventional liquid chromatography and analysis on a tandem mass spectrometer equipped with a heated nebulizer ion source. Epitestosterone does not interfere with this liquid chromatography tandem mass spectrometry (LC-MS/MS) method for total testosterone.(Unpublished Mayo method)
Free Testosterone:
This method utilizes equilibrium dialysis to analyze and determine the host serum’s binding capacity for testosterone. Patient sample is placed inside a dialysis well that is immersed in dialysis buffer. The sample is dialyzed. During buffered dialysis, any testosterone that is unbound to sex hormone-binding globulin (SHBG) or albumin is free to pass through the semi-permeable dialysis membrane, while testosterone molecules bound to the binding proteins will be held inside the membrane.
After dialysis, the buffered dialysate is analyzed for free testosterone by LC-MS/MS with stable isotope (testosterone-[13]C3) after derivatization.(Unpublished Mayo method)
