Testosterone is the most abundant sex steroid in women by volume - more than estradiol at almost every point in the cycle. It peaks in your early twenties and declines roughly 50% by forty. And yet it is almost never ordered on a women's panel.
The cultural association of testosterone with men has created a diagnostic blind spot. Women with low testosterone report flat libido, muscle loss despite consistent training, cognitive fog, and a motivational flatness that doesn't respond to antidepressants because it isn't depression - it's a hormone. The biomarker that explains it sits untested.
What testosterone does in women
Testosterone is produced in the ovaries, the adrenal glands, and peripheral fat tissue. In the brain, it supports dopamine signalling, which governs motivation, focus, and reward. In muscle, it's anabolic - it maintains lean mass and prevents the accelerated loss that tracks perimenopause. In bone, it works alongside estradiol to preserve density. In the clitoris and vulva, it drives sensitivity and arousal.
- Libido and sexual sensitivity - the most commonly reported deficit when levels are low.
- Muscle mass and strength - testosterone loss is a primary driver of perimenopausal sarcopenia.
- Cognitive focus and motivation - acts via dopamine; often mistaken for burnout or depression.
- Bone density - independent of estrogen's contribution.
- Mood stability - particularly in the luteal phase when it naturally dips.
The testing problem
Most standard serum testosterone assays were designed and validated on male reference ranges. When a woman's result is reported against a male normal, the lower end of the male range looks reassuringly normal but is actually deficient for a woman. This is not a minor calibration issue - it's a systematic misread that leaves low testosterone invisible on standard labs.
Who is most at risk
Women on oral contraceptives
Combined oral contraceptives suppress ovarian testosterone production by roughly 40–60% and simultaneously raise SHBG, which binds whatever remains. The net effect on free testosterone can be profound and, for some women, persists months after stopping the pill - the so-called 'post-pill SHBG lag.'
Women in perimenopause
Ovarian testosterone output declines through the menopause transition. The adrenal contribution (via DHEA-S conversion) also falls with age. By the time formal menopause is reached, total testosterone is typically 25–50% of peak-reproductive levels.
Women who have had oophorectomy
Bilateral oophorectomy removes roughly 50% of total testosterone production at any age. Surgical menopause without testosterone replacement leaves a gap that estrogen alone does not fill.
What to order
The minimum useful panel is: free testosterone by equilibrium dialysis, total testosterone, and SHBG. Add DHEA-S to assess the adrenal upstream contribution. If DHEA-S is low, the problem starts above the ovaries.
Timing matters: testosterone is highest in the morning and in the follicular phase. A midday draw in the luteal phase will read low relative to a morning follicular draw - not because levels changed, but because the window shifted. Standardise your draw conditions when tracking over time.