Different hair follicles respond to DHT differently. Some respond by accelerated hair growth, some with shrinking hair follicles, and others are non responsive (the ones that get transplanted from the back of your head in hair transplants). The hair on top of your head will have a follicle that declines in size in response to DHT exposure. This means people with androgenic alopecia, whom are hypersensitive, will lose their hair quicker. Using finasteride will inhibit DHT production, meaning that hair will stop falling out as quickly because there is less DHT available to stimulate the hair follicles atop your head.
At least, that's the gist of what I looked up.