Male and female pattern baldness has been characterized as an androgen-based miniaturization process of hair follicles that are susceptible to a certain gene called dihydrotestosterone (DHT).
Pattern baldness is caused by the hormone DHT attacking the hair follicles. DHT is a conversion of testosterone by the enzyme 5-alpha reductase. DHT attacks these genetically susceptible hair follicles and causes hair miniaturization until these follicles ultimately reach death.
Donor versus recipient grafts refers to the hair grafts taken from the donor area to grow and survive after transplantation to the frontal area of alopecia. Even regular levels of testosterone can be converted to high levels of DHT, or the hair follicle itself can be abnormally receptive to DHT and therefore create advanced cases of androgenic alopecia. Fortunately, the follicles taken from the donor areas have little to no enzyme and therefore are not affected by the DHT.