Male pattern hair loss, or androgenetic alopecia (AGA), is the most common type of hair loss among males. Hormonal factors appear to play a role, especially a male sex hormone known as dihydrotestosterone (DHT).
Hair loss affects around half of all men over the age of 50 years, and around 50 million men in the United States (U.S.).
Male pattern hair loss is the most common type of hair loss in men. Hair at the temples and on the crown slowly thin and eventually disappear. The exact reason why this happens is unknown, but genetic, hormonal, and environmental factors are all thought to play a role. DHT is believed to be a major factor.
Male pattern hair loss happens when the follicles slowly become miniaturized, the anagen phase is reduced, and the telogen phase becomes longer.
Over time, the anagen phase becomes so short that the new hairs do not even peek through the surface of the skin. Telogen hair growth is less well-anchored to the scalp, making it easier to fall out.
As the follicles become smaller, the shaft of the hair becomes thinner with each cycle of growth. Eventually, hairs are reduced to vellus hairs, the type of soft, light hairs you can see on infants and they mostly disappear during puberty in response to androgens.
How DHT affects hair growth
The hair on the head grows without the presence of DHT, but armpit hair, pubic hair, and beard hair cannot grow without androgens. DHT is a normal part of male physiology and is important for development. While blocking conversion of testosterone to DHT with pharmaceuticals like finasteride can be useful for hair loss in men, this is associated with sexual side effect. Natural ingredients like saw palmetto and lycopene have similar effects but their efficacy compared to finasteride is low. Consult with a board certified dermatologist if you would like to explore finasteride treatment.