These changes typically begin gradually in men in their 20s.
Androgenic alopecia is the most common cause of baldness in men and women.
The two major factors in androgenic alopecia are genetics and hormones. For a person to develop male pattern baldness, they need both of these factors to have hair loss. A subgroup of these eunuchs were given testosterone at 50 years of age and the eunuchs with a genetic propensity to bald did exactly that. How we discovered this is there is a family with a genetic defect in Alpha-5 Reductase. Without this enzyme, the male family members do not produce DHT and they never go bald.