Testosterone in women: the overlooked hormone that changes everything.
Women produce testosterone. It has profound effects on energy, libido, muscle, and mood. And almost nobody measures it.
When women hear "testosterone", they usually think of it as a male hormone, something they have in small amounts that doesn't really matter. This is one of the most consequential misconceptions in women's health.
Women produce testosterone primarily in the ovaries and adrenal glands. The amount is roughly ten times lower than in men, but it acts on the same receptors, in the same tissues, with many of the same effects. And when it declines (which it does steadily from the mid 20s, with a sharper drop at perimenopause) the consequences are real, measurable, and often dismissed.
What testosterone does in women.
- Energy and motivation: testosterone contributes to drive, initiative, and resistance to fatigue.
- Libido: testosterone is the primary driver of sexual desire in women, and the evidence is unambiguous.
- Muscle maintenance: low testosterone accelerates the loss of lean mass, particularly through the 40s.
- Bone density: testosterone stimulates osteoblast activity, and low T is independently associated with osteoporosis.
- Mood: testosterone receptors in the prefrontal cortex influence confidence, mood stability, and stress resilience.
- Cognitive function: executive function, verbal memory, and spatial reasoning all depend, in part, on testosterone.
The problem with measurement.
Standard testosterone tests are calibrated for men. The ranges are built on male reference populations. A woman at the bottom of a male reference range has a profoundly different hormonal picture than a man at the same number.
A woman with free testosterone of 0.4 pg/mL (technically "within range") may experience significant symptoms if her level was 1.2 pg/mL a year ago. You cannot interpret a number without a baseline.
This is exactly why we track trends over time: not just where you are, but where you have been.
Perimenopause and the accelerated decline.
Testosterone in women drops gradually from the 20s, but perimenopause (which can begin as early as 38 to 42) accelerates the decline. It often precedes the oestrogen drop by several years, meaning many women experience fatigue, low libido, mood changes, and reduced motivation years before they would consider themselves "menopausal".
A study in the Journal of Clinical Endocrinology and Metabolism found that premenopausal women in the lowest quartile of testosterone were significantly more likely to report reduced quality of life, fatigue, and depressed mood, at an average age of 38.
What we test.
We measure total testosterone, free testosterone, and SHBG together. Total testosterone alone is often misleading: high SHBG binds more testosterone, leaving less of the active form available to your cells. You can have a normal total T and low free T, and feel every bit of it.
