Testosterone / estradiol (T:E2) ratio

The balance between testosterone and estradiol in men, showing how much testosterone is converted into estrogen by the enzyme aromatase.

Also known as: T to E2 ratio, testosterone estrogen ratio, T:E2

Testosterone and estradiol work in balance. In men, a small share of testosterone is continuously converted into estradiol, the main estrogen, by the enzyme aromatase, which is most active in fat tissue. The T:E2 ratio compares the two hormones and shows how strongly this conversion is running. A low ratio means relatively more estradiol. Common drivers are excess body fat, regular alcohol use, reduced liver clearance and low testosterone production itself. In men this pattern can contribute to reduced libido, difficulty building muscle, fatigue, mood changes and breast tissue growth. A high ratio points to too little estradiol relative to testosterone, which matters for bone strength, joints and sexual function even when testosterone itself looks fine. Body fat, alcohol, sleep and training all influence the ratio, so it often improves with the same habits that support healthy testosterone. We calculate it from testosterone and estradiol measured in the same molar unit (pmol/l). Ranges quoted in US units (ng/dL divided by pg/mL) are roughly 9 times lower than values on this scale.