Dihydrotestosterone has twice as much impact on the prostate as does testosterone, and to get DHT, testosterone must be converted by the enzyme 5-alpha reductase. Although testosterone levels naturally decline in men as they age, DHT concentrations in the prostate remain at levels similar to those in young men. One more hormone, estrogen (estradiol), also may have a role in BPH.
Estradiol levels remain relatively the same or even increase as men age, especially if there is an increase in body fat. That’s because fat cells contain an enzyme that converts some androgens to estrogen. A disproportionate estrogen/testosterone ratio may contribute to the development of an enlarged prostate.