In order to clarify and harmonise ordering of testosterone requests across Awanui Labs, a change to the number of testosterone request options will be effective from 17th Sept 2024. These changes will have no impact on clinical management of patients but will make testosterone ordering simpler.
The current multiple different total testosterone request options will be consolidated into 4 options:
E-Ordering – options available when searching for Testosterone
1.SHBG (Sex Hormone Binding Globulin) – Code [SHB]
- This option will include SHBG only
- If total testosterone is also required, select combined [Testosterone + SHBG]
2. Testosterone only – Code [TESF]
- This option will report Total Testosterone only and will NOT INCLUDE either SHBG or any calculations (see below).
3. Testosterone + SHBG – Code [FAI]
- This option will routinely include, in addition to Total Testosterone:
- Sex Hormone Binding Globulin (SHBG), and
- Calculation(s):
- Calculated Free Testosterone (Vermeulen equation),
- Calculated Free Androgen Index
- Please note: Free Androgen Index will NOT be reported if total testosterone concentration is high (>52 nmol/L) and/or if SHBG concentration is low (<13 nmol/L) as the calculation becomes unreliable under these conditions.
The Roche Elecsys Testo II competitive immunoassay’s excellent precision (total imprecision <6%), low limit of detection (0.087 nmol/L), and functional sensitivity of 0.416 nmol/L shows comparable performance to the LC-MS/MS for males, and improved performance for females and children compared to older 1st generation assays, and provides a very reliable measure of total testosterone for most clinical conditions characterised by low or high testosterone levels (hypogonadism, hyperandrogenism, or androgen-secreting tumours) and for the monitoring of testosterone hormone replacement therapy. The Roche Elecsys Testo II immunoassay also provide a quicker turnaround time and is routinely available from all Awanui laboratories.
- Measurement of SHBG is always recommended when total testosterone concentrations are low or borderline, particularly in obese or older men.
- The Free Testosterone (Vermeulen equation) calculation in male patients may be helpful in borderline testosterone cases.
- The Free Androgen Index calculation is known to give erroneous results in male patients and will not be reported for total testosterone >52 nmol/L and/or SHBG <13 nmol/L.
- In females, at least 80% of bound serum testosterone is bound to SHBG. Consequently, free serum testosterone will be influenced by SHBG concentrations, which will limit the interpretation of the calculated Free Testosterone concentration in female patients. The Free Androgen Index calculation takes this SHBG dependence into account.
- Although the Free Androgen Index is known to give erroneous results in male patients with total testosterone concentrations >52 nmol/L, it is still widely used for the investigation of hyperandrogenism and androgenic alopecia in female patients.
- The Free Androgen Index calculation however, is also not a reliable indicator of free testosterone concentrations when the SHBG concentration is low, and could lead to misleading information in a large number of female patients being investigated for hyperandrogenism and will therefore note be reported if SHBG <13 nmol/L.
4. Testosterone-LCMS (Specialist only) – Code [LCM]
The Testosterone-LCMS assay is a liquid chromatography tandem mass spectrometry, high sensitivity and specificity assay that is indicated when testosterone levels are expected to be below the normal male range, such as when used for the evaluation/monitoring of:
- Congenital conditions resulting in decreased testosterone production such as:
- Klinefelter syndrome
- Kallmann syndrome
- Prader-Willi syndrome
- Hypogonadal men:
- Primary hypogonadism (testicular failure)
- Secondary hypogonadism (inadequate stimulation by pituitary gonadotropins)
- Testicular damage due to alcoholism, physical injury, viral disease (mumps) and in certain malignancies
- Patients on androgen deprivation therapy
Please note:
- Samples for testosterone on LC-MS/MS are batched and performed only twice a week.
- SHBG will NOT be reflexed on this option regardless of the testosterone result because:
- SHBG is performed on a different platform, and
- Patients will need a rebleed due to differing sample type requirements.
- Free testosterone and the Free Androgen Index will also NOT be calculated on this option for the same reasons.
- Awanui is currently the only laboratory in New Zealand offering testosterone on LC-MS/MS and routine use of this specialised and resource intensive method for first line assessment of androgen status can no longer be justified or supported especially since all other public and private laboratories, including Canterbury Health Labs and LabPlus in regions outside of Otago & Southland, performed testosterone measurements on immunoassay methodology only.
- All future LCMS testosterone requests outside of these indications above will require a clear clinical justification as well as specialist or pathologist approval. Please enter details in e-ordering:
What’s in a name? Demystifying testosterone
Total testosterone (TT) signifies the total pool of testosterone available in the human body and consists largely of bound testosterone (majority) and a small proportion of free testosterone (FT), which is biologically active. Bound testosterone can be further subdivided into testosterone bound to sex hormone binging globulins (SHBG) – a strong bond, and testosterone bound to albumin – a relatively weak bond. Bioavailable testosterone includes both free and albumin-bound testosterone, which comprise the non-SHBG bound proportion.
In women the concentration of SHBG usually greatly exceeds the total testosterone (TT) level and very little free testosterone is present. The amount of free testosterone in women can be roughly estimated as a simple ratio of total testosterone to SHBG, also known as the Free Androgen Index (FAI) – FAI = TT (nmol/L) x 100 / SHBG (nmol/L). However, if TT levels are similar or greater than SHBG levels, as in men, the amount of FT will be higher, even after accounting for some albumin binding of steroid hormones. For these reasons, the FAI may then become unreliable. This applies when either TT levels are high (e.g. normal men) or when SHBG levels are low (e.g. in insulin resistance including most women with PCOS).
Please note that calculated FT (cFT) is not the same as an empirical formula called “bioavailable testosterone” that tries to predict the concentration of non-SHBG bound testosterone following laboratory precipitation of binding proteins.
Because there is a diurnal variation of testosterone with higher levels in the morning (particularly in men), samples should be taken between 8am and 10am. Whether fasting or intermittent fasting and low-calorie diets (energy restriction) improve, or lower testosterone levels, are still under a lot of debate.
Dr Melissa Yssel
Clinical Lead – Chemical Pathology Awanui labs
03/09/2024
References:
- Sikaris, K (May 2007). Insight – Free Testosterone. https://www.mps.com.au/media/6473/free-testo-may-07.pdf
- Blume-Peytavi U et al. S1 guideline for diagnostic evaluation in androgenic alopecia in men, women and adolescents. Br J Dermatol. 2011;164(1):5-15 https://pubmed.ncbi.nlm.nih.gov/20795997/
- Keevil BG, Fiers T et al. The free androgen index is inaccurate in women when the SHBG concentration is low. Clin Endocrinol (Oxf.). 2018 May;88(5):706-710 https://onlinelibrary.wiley.com/doi/10.1111/cen.13561
- Agretti P, Pelosini C, Bianchi L et al. Importance of total and measured free testosterone in diagnosis of male hypogonadism: immunoassay versus mass spectrometry in a population of healthy young/middle-aged blood donors. J Endocrinol Invest. 2021 Feb,44(2):321-326 https://pubmed.ncbi.nlm.nih.gov/32474765/
- Brandhorst G et al. Multicenter evaluation of a new automated electrochemiluminescence immunoassay for the quantification of testosterone compared to liquid chromatography tandem mass spectrometry. Clin Biochem. 2011 Feb, 44(2-3):264-267