Welcome to part 4 of the ODX Andropause & Low T Syndrome Series. In this post, the ODX Research team reviews the best biomarkers to test and the ranges to use in order to get an accurate assessment and diagnosis of Andropause or Low T Syndrome.
Identifying and treating LOH is imperative due to its close association with morbidity and mortality. Knowing which biomarkers to test and their ranges is paramount.
Prospective data analysis of 2599 subjects in the EMAS revealed[i]
It is important to measure T in the morning as levels peak at that time. Measurement between 7 and 11 am is customary.[ii] Consistently testing levels at 8 am is prudent with repeat levels taken ~30 days apart.
It is also important to obtain a fasting level as food intake and glucose suppress T levels.[iii] Even in individuals with normal glucose tolerance, a glucose load can reduce TT by 15-30%.[iv] Serum T levels can also vary seasonally.[v]
Reference ranges for serum total and free T can vary due to lack of standardized assays, calibration variations, and differences in a reference population. As always, it is important to utilize the same laboratory when repeating blood work.
If serum levels are near low normal, or if SHBG levels are altered, assessment of free testosterone via equilibrium dialysis or calculation (using TT, SHBG, and albumin) is warranted. Direct analog-based free testosterone immunoassays may be inaccurate.[vi]
Harmonized ranges for total T for healthy non-obese men 19-39 years old according to the CDC and adopted by the Endocrine Society:[vii] [viii]
264-916 ng/dL 9.2-31.8 nmol/L using 2.5th and 97.5 percentile
303-852 ng/dL 10.5-29.5 nmol/L using 5th and 95th percentile
Mean normal testosterone in young adults is ~627 ng/dL (21.8 nmol/L). Researchers suggest that a T level 2.5 standard deviations below the mean should define hypogonadism, i.e., a level of 319 ng/dL (11 nmol/L). Researchers note that levels below 300 ng/dL are associated with reduced bone mineral density.[ix]
Testosterone levels below those of a healthy young male adult in a symptomatic individual should be evaluated. Values of TT below 400 ng/dL warrant further evaluation especially when coupled with symptoms that interfere with wellbeing. Once levels drop below 250 ng/dL, all-cause mortality risk doubles.[x]
Although individual levels can vary, total serum T may slowly decline with age from a mean of 600 ng/dL (20.8 nmol/L) at age 40 to 400 ng/dL (13.9 nmol/L) at age 80. Since testosterone bound to SHBG is not considered bioavailable, total levels can remain within the normal range but symptoms may persist if SHBG is elevated. Assessment of free and bioavailable T and correlation with symptoms can help determine LOH on an individual basis.[xi]
As the fraction of testosterone tightly bound to SHBG increases, its availability to cells and tissues decreases.
Bioavailable testosterone (BAT) is considered that fraction not bound to SHBG. Technically, it includes free T and that bound to but easily dissociated from albumin, as well as that bound to CBG and orosomucoid. However, assessment methods define bioavailable T as free T plus albumin-bound T.[xii]
Free T can be difficult to measure accurately and is most often estimated through calculation using TT, SHBG, and albumin levels.[xiii]
Total T
Free T
Bioavailable T
Calculators
If available, equilibrium dialysis is considered the gold standard for measuring free T, while precipitating out SHBG-testosterone using ammonium sulfate is considered the gold standard for measuring BAT.
A prospective observational study of 51 men 55-70 years old found that TT measurement and calculated free T (using TT, albumin, and SHBG) correlated best with gonadal function and clinical symptoms of androgen deficiency. Researchers discouraged the use of direct measurement of free T and/or calculation of free androgen index/FAI for diagnosing androgen deficiency in this age group as neither measurement was a reliable reflection of free T.[xix]
Assessment of BAT is especially useful in subjects who are obese and/or 70 years or older. Researchers note a 35% reduction in TT is observed in men from age 25 to 75, and a 50-60% reduction in BAT is observed from 25 to 75.[xx]
A cross-sectional observational study of 608 males over age 45 found that severity of symptoms correlated with low calculated free and bioavailable T but not with total T. Men with hypertension were noted to have free and bioavailable T levels that were significantly lower than men without hypertension. Researchers observed mean free T levels associated with LOH at levels higher than defined by EMAS which has a cutoff of 64 pg/mL (220 pmol/L):[xxi]
NEXT UP: Andropause Part 5 – Clinical Determination
[i] Pye, S R et al. “Late-onset hypogonadism and mortality in aging men.” The Journal of clinical endocrinology and metabolism vol. 99,4 (2014): 1357-66. doi:10.1210/jc.2013-2052
[ii] Singh, Parminder. “Andropause: Current concepts.” Indian journal of endocrinology and metabolism vol. 17,Suppl 3 (2013): S621-9. doi:10.4103/2230-8210.123552.
[iii] Bhasin, Shalender et al. “Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.” The Journal of clinical endocrinology and metabolism vol. 103,5 (2018): 1715-1744. doi:10.1210/jc.2018-00229
[iv] Giagulli, Vito Angelo et al. “Critical evaluation of different available guidelines for late-onset hypogonadism.” Andrology vol. 8,6 (2020): 1628-1641. doi:10.1111/andr.12850
[v] Decaroli, Maria Chiara, and Vincenzo Rochira. “Aging and sex hormones in males.” Virulence vol. 8,5 (2017): 545-570. doi:10.1080/21505594.2016.1259053
[vi] Bhasin, Shalender et al. “Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.” The Journal of clinical endocrinology and metabolism vol. 103,5 (2018): 1715-1744. doi:10.1210/jc.2018-00229
[vii] Bhasin, Shalender et al. “Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.” The Journal of clinical endocrinology and metabolism vol. 103,5 (2018): 1715-1744. doi:10.1210/jc.2018-00229
[viii] Giagulli, Vito Angelo et al. “Critical evaluation of different available guidelines for late-onset hypogonadism.” Andrology vol. 8,6 (2020): 1628-1641. doi:10.1111/andr.12850
[ix] Mulligan, T et al. “Prevalence of hypogonadism in males aged at least 45 years: the HIM study.” International journal of clinical practice vol. 60,7 (2006): 762-9. doi:10.1111/j.1742-1241.2006.00992.x
[x] Dudek, Piotr et al. “Late-onset hypogonadism.” Przeglad menopauzalny = Menopause review vol. 16,2 (2017): 66-69. doi:10.5114/pm.2017.68595
[xi] Rogers, Linda C. "The role of the laboratory in diagnosing andropause (male menopause)." Laboratory Medicine 36.12 (2005): 771-773.
[xii] Goldman, Anna L et al. “A Reappraisal of Testosterone's Binding in Circulation: Physiological and Clinical Implications.” Endocrine reviews vol. 38,4 (2017): 302-324. doi:10.1210/er.2017-00025
[xiii] Goldman, Anna L et al. “A Reappraisal of Testosterone's Binding in Circulation: Physiological and Clinical Implications.” Endocrine reviews vol. 38,4 (2017): 302-324. doi:10.1210/er.2017-00025
[xiv] Bhasin, Shalender et al. “Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline.” The Journal of clinical endocrinology and metabolism vol. 103,5 (2018): 1715-1744. doi:10.1210/jc.2018-00229
[xv] Keevil, Brian G, and Jo Adaway. “Assessment of free testosterone concentration.” The Journal of steroid biochemistry and molecular biology vol. 190 (2019): 207-211. doi:10.1016/j.jsbmb.2019.04.008
[xvi] Goldman, Anna L et al. “A Reappraisal of Testosterone's Binding in Circulation: Physiological and Clinical Implications.” Endocrine reviews vol. 38,4 (2017): 302-324. doi:10.1210/er.2017-00025
[xvii] Decaroli, Maria Chiara, and Vincenzo Rochira. “Aging and sex hormones in males.” Virulence vol. 8,5 (2017): 545-570. doi:10.1080/21505594.2016.1259053
[xviii] International Society for the Study of the Aging Male. Free and bioavailable T calculator
[xix] Christ-Crain, M et al. “Comparison of different methods for the measurement of serum testosterone in the aging male.” Swiss medical weekly vol. 134,13-14 (2004): 193-7.
[xx] Clapauch, Ruth et al. “Laboratory diagnosis of late-onset male hypogonadism andropause.” Arquivos brasileiros de endocrinologia e metabologia vol. 52,9 (2008): 1430-8. doi:10.1590/s0004-27302008000900005 [R}
[xxi] Liu, Zhangshun et al. “Comparing calculated free testosterone with total testosterone for screening and diagnosing late-onset hypogonadism in aged males: A cross-sectional study.” Journal of clinical laboratory analysis vol. 31,5 (2017): e22073. doi:10.1002/jcla.22073