What Is Testosterone?
Testosterone is a steroid hormone essential in both sexes for energy, mood, body composition, bone density, libido, cardiovascular health, and cognitive function.
A complete assessment measures:
- Total testosterone — all testosterone, bound and unbound
- Free testosterone — the ~2–3% that is biologically active
Why Both Forms Matter
You can have normal total testosterone with low free testosterone if SHBG is elevated. Testing total testosterone alone misses part of the picture.
What Testosterone Affects
In men: energy, muscle mass, fat distribution, mood, libido, bone density, red blood cell production.
In women: energy, libido, mood, muscle maintenance, bone density. Low testosterone in women is frequently unrecognized.
Reference Ranges
Men: Below 8 nmol/L: Low. 8–12: Low-normal. 12–30: Normal. 20–29: Optimal.
Women: Below 0.5 nmol/L: Low. 0.5–2.4: Normal.
What Causes Low Testosterone?
- Age — ~1–2% decline per year after 30
- Chronic stress — cortisol suppresses testosterone
- Poor sleep
- Obesity/visceral fat — aromatase converts testosterone to estrogen
- Overtraining without recovery
How to Optimize Testosterone
- Sleep quality — 7–9 hours consistently
- Resistance training
- Managing body fat
- Stress management
- Zinc and vitamin D
Is Testosterone Tested in a Standard Physical?
Rarely. Stem Health tests total and free testosterone in every Core and Horizon Assessment.
