Does lower total testosterone indicate lower overall androgen availability in women?

In women, the circulating testosterone pool is a complex composite of glandular secretion and peripheral metabolism, though the measurement of "total testosterone" alone may not provide a complete picture of biological androgen activity.

Sources of Circulating Testosterone

Circulating testosterone in women is derived from a tripartite model of production involving direct secretion and metabolic conversion. Scientific consensus identifies three primary sources:

• Direct Glandular Secretion: The ovaries and the adrenal glands each contribute approximately 25% of the total circulating testosterone pool through direct synthesis.
• Peripheral Conversion: The remaining 50% is produced through the peripheral conversion of pro-androgens, primarily androstenedione, which are secreted by both the adrenal glands and ovaries and subsequently processed in non-endocrine tissues.
• Mechanistic Regulation: Direct ovarian production is regulated by gonadotropins (LH and FSH) within the theca cells, while peripheral conversion is mediated by 17β-hydroxysteroid dehydrogenase enzymes located throughout the body. This distributed model explains why the removal of a single source (such as through oophorectomy) significantly reduces but does not entirely eliminate circulating testosterone.

Clinical Utility of Total Testosterone

While total testosterone represents the absolute quantity of the hormone in the blood, its reliability as an indicator of overall androgen availability is limited by several biological factors:

• Bioavailability and SHBG: Total testosterone does not account for Sex Hormone-Binding Globulin (SHBG). Because SHBG binds tightly to testosterone, only the "free" or bioavailable fraction is biologically active. During the menopausal transition, SHBG levels can fluctuate significantly, decoupling total testosterone levels from actual tissue exposure.
• Clinical Predictors: Research indicates that bioavailable testosterone and the Free Androgen Index (FAI) are far stronger predictors of clinical outcomes—such as bone mineral density and visceral fat accumulation—than total testosterone alone.
• Relative Androgenicity: The testosterone-to-estradiol ratio often serves as a better predictor of metabolic health and syndrome risk than absolute total testosterone concentrations.

Bottom line

While it is factually correct that female testosterone originates from ovarian, adrenal, and peripheral sources, a lower total testosterone measurement is a blunt tool that may not accurately reflect cellular androgen availability. In clinical practice, assessing free or bioavailable testosterone is essential to account for the confounding effects of SHBG and provide a true representation of androgenic status.