A man with a receding hairline.
The problem of receding hairline in men, also called male pattern baldness, stems from a medical condition known as androgenetic alopecia, which occurs when the hair follicles on a man’s scalp thin and eventually stop growing again. The condition can usually be identified by the thinning of the hair on a man’s head and the subsequent formation of a hairline with an M pattern where it remains. It can also recede further into a horseshoe shape, where the center of the scalp is exposed and the hair remains only on the back and sides of the head. This type of baldness is common in older men, but age is not the only cause. The other two known reasons for male pattern baldness are genes and hormonal changes.
Aging increases the risk of male pattern baldness.
There is a strong coincidence between age and hairline retraction in men. About 25% of men over the age of 30 begin to lose hair, and by age 60 it increases to over 60%. Age, however, only raises the risk of male pattern baldness and determines when it starts; in rare cases, it also happens to teenagers. Although age is popularly considered the main cause of progressive hair loss, it is more of a contributing factor or a catalyst for other underlying factors.
About a quarter of men begin to lose hair after age 30.
Hormonal changes are one of the underlying causes of hairline receding in men. At some point in a man’s life, his body produces an enzyme called 5-alpha reductase, which binds to the male hormone known as androgen. This interaction results in the production of dihydrotestosterone (DHT), another form of the male sex hormone. DHT partially blocks vitamins and proteins from reaching the hair follicles, and as a result, the hair in the affected follicle will not grow as long or as thick as it once did. Eventually, the hair follicle starves to death from lack of nutrition due to a complete blockage, and the hair that falls out does not grow back.
Changes in hormones often result in hairline indentation in men.
Genetic inheritance is another important factor that affects the onset of hair loss. The gene known as androgen receptor (AR) was the first gene to be specifically identified as the cause of hairline indentation in men. The stronger the AR gene, the earlier and more pronounced the hair loss. Originally, the AR gene responsible for hair loss was identified as being passed on from mother to child, but more recent studies have shown that it can also be inherited from the father. Other research has identified another gene on the 20th chromosome that can trigger male pattern baldness, even for men who don’t have a strong AR gene.