A receding hairline is a loss of hair just above the temples. It usually follows a pattern similar to the letter "M." The hair along the sides and middle of the head remains intact while the hair loss progresses up along the lateral sides of the forehead. Over time, this hair loss may eventually spread across the top of the head, but this depends on the person as well as the cause of the receding hairline.
A common cause of receding hairlines is age. The National Institutes of Health explains that people experience a thinning of hair as they grow older, so it isn't uncommon to see a recession along the hairline as you advance in years. Approximately 66 percent of men have a balding pattern, or suffer from baldness, by the age of 60, and 25 percent of men begin to encounter hair loss by the age of 30.
Another contributing factor to a receding hairline is heredity. In this situation, it's an inherited trait from your mother or father that causes the hairline to recede. The American Hair Loss Association claims that most hair loss in men is associated with heredity. The follicles along the scalp, especially those along the lateral sides of the forehead, are genetically sensitive to dihydrotestosterone (DHT). DHT can cause the hair to recede. Without this genetic trait, you most likely won't suffer from a receding hairline until you get older.
The third factor that causes receding hairlines is testosterone, notes the National Institutes of Health. Without this androgen, a man can't develop male-pattern baldness, which includes the receding hairline. Testosterone exposed to type II 5alpha-reductace converts into dihydrotestosterone, according to the American Hair Loss Association. When DHT comes into contact with hair follicles, it causes them to shrink in size. This shrinkage affects the growth of the hair, producing finer hairs than normal. These hairs easily fall out. Normally, another hair replaces those that are shed. But DHT prevents hair growth, which leads to a receding hairline. If you lacked testosterone, this whole process couldn't take place.