The most likely cause of male pattern baldness is an inherited sensitivity to dihydrotestosterone (DHT). This is a natural substance produced around hair follicles, and in response to the genetic trigger, it has a negative effect on hair growth, causing a shortening of the hair growth phase. As a result, hair is thinner and hair follicles are smaller. In combination, this disruption in the hair growth cycle results in lower numbers of the longer and thicker hairs that normally grow on the scalp.