Pattern balding or thinning refers to the inherited pattern of hair loss genetically passed down from either side of the family. It is caused when hair follicles are oversensitive to the male hormone, dihydrotestosterone (DHT). This causes the hair to become thinner and shorter.
The reason men go bald is due to the chemical makeup of their hair. The hair on top of the scalp has higher levels of the enzyme 5 alpha reductase (5AR) that causes an increase in the naturally occurring hormone dihydrotestosterone (DHT). DHT miniaturises the hair over time, gradually, in many cases until none is left and the head becomes shiny bald (the most severe cases).
The hair at the back of the scalp (known as ‘permanent hair’) naturally has lower levels of DHT so this hair does not commonly fall out.
MPB may skip a family member or even a generation and starts sometime after puberty.