This affects up to 80% of men by the age of 80. It is a condition caused by age, genetics and a specific hormone called DHT (dihydrotestosterone) that attacks hair follicles leading to a disruption of the normal hair growth cycle. This disruption causes follicles to shrink and grow at a slower pace, eventually leading to the hair falling out and the pattern repeating itself with other hair follicles in other parts of the scalp. This process can affect the entire scalp, except for the hair at the back and sides of the head, which is not subject to male pattern baldness. This is a genetically permanent zone, which makes it a viable solution to be used for hair transplant surgery.