Measuring free testosterone provides information about how much active unbound testosterone is in circulation, a level that can be influenced by sex hormone binding globulin (SHBG), insulin resistance, and BMI.
Higher free testosterone in women is associated with PCOS, hirsutism, virilization, abdominal adiposity, and increased severity of fatty liver disease, while lower levels are associated with lower libido and decreased sexual function.
Standard Range: Female 0.10 - 6.4 pg/mL (0.35 - 22.19 pmol/L)
The ODX Range: Female 3.25 – 4.6 pg/mL (11.27 – 15.95 pmol/L)
PLEASE NOTE: The ranges above are derived using the Vermulein calculator that calculates free testosterone from Albumin, Sex Hormone Binding Globulin, and Total testosterone. The ODX platform uses this calculation in the analytical software. CLICK HERE to access the calculator in this site's calculators section. CLICK HERE to read a post we made on why NOT to measure Free Testosterone in favor of using the Vermulein calculator.
Low levels of free testosterone may be associated with decreased libido and decreased sexual function index scores (Turna 2005).
High levels of free testosterone have been associated with PCOS, and increased severity of NAFLD, NASH, fibrosis, and abdominal adiposity in premenopausal women (Sarkar 2021). Measuring free testosterone in females also assists in the evaluation of hirsutism and virilization. Circulating free to total testosterone in hirsutism may be double that of women without hirsutism (Sowers 2001).
Free testosterone (FT) levels are evaluated during the assessment of androgen excess, PCOS, subfertility, and insulin resistance in women.
A free testosterone level of 8.4 pg/mL (29 pmol/L) or above can be considered hyperandrogenemia in women (Song 2017). However, one study of subfertile women with suspected PCOS used a lower FT cut-off of 4.9 pg/mL (17 pmol/L) or above as indicative of androgen excess. In this study, a FT above 4.9 pg/mL was associated with increasing BMI, serum insulin, and insulin resistance. Higher FT was also associated with increased total testosterone, androstenedione, LH, and LH/FSH, as well as decreased SHBG (Antonio 2018).
One study of premenopausal women with biopsy-confirmed non-alcoholic fatty liver disease found that an increasing free testosterone was independently associated with increased severity of NAFLD, fibrosis, steatohepatitis, and abdominal obesity. The presence of PCOS may have driven some of the associated liver dysfunction. However, the association of higher free testosterone and severity of liver disease was present in those without PCOS as well (Sarkar 2021).
Free testosterone levels were found to correlate with sexual desire and function in women. Low libido and lower sexual function index scores were associated with significantly lower levels of free testosterone, total testosterone, and DHEA-S in premenopausal and postmenopausal women compared to controls (Turna 2005).
Antonio, L et al. “Free Testosterone Reflects Metabolic as well as Ovarian Disturbances in Subfertile Oligomenorrheic Women.” International journal of endocrinology vol. 2018 7956951. 10 Sep. 2018, doi:10.1155/2018/7956951
Davis, Susan R., and Sarah Wahlin-Jacobsen. "Testosterone in women—the clinical significance." The Lancet Diabetes & Endocrinology 3.12 (2015): 980-992.
Sarkar, Monika A et al. “Testosterone is Associated With Nonalcoholic Steatohepatitis and Fibrosis in Premenopausal Women With NAFLD.” Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association vol. 19,6 (2021): 1267-1274.e1. doi:10.1016/j.cgh.2020.09.045
Song, Do Kyeong et al. “Differentiation between polycystic ovary syndrome and polycystic ovarian morphology by means of an anti-Müllerian hormone cutoff value.” The Korean journal of internal medicine vol. 32,4 (2017): 690-698. doi:10.3904/kjim.2016.038
Sowers, M F et al. “Testosterone concentrations in women aged 25-50 years: associations with lifestyle, body composition, and ovarian status.” American journal of epidemiology vol. 153,3 (2001): 256-64. doi:10.1093/aje/153.3.256
Turna, B et al. “Women with low libido: correlation of decreased androgen levels with female sexual function index.” International journal of impotence research vol. 17,2 (2005): 148-53. doi:10.1038/sj.ijir.3901294