Male pattern hair loss, also called androgenetic alopecia, is a common form of hair loss. MedlinePlus Genetics says it is known in men as male pattern baldness and that researchers have determined it is related to hormones called androgens, specifically dihydrotestosterone (DHT). This guide covers what the sources say about the pattern, what drives it and how it is told apart from other causes.
What it is and how common it is
The MedlinePlus Genetics page estimates that androgenetic alopecia affects 50 million men and 30 million women in the United States. The same page says it can start as early as a person's teens, that the risk increases with age, and that more than 50 percent of men over age 50 have some degree of hair loss.
A 2002 review (Expert Rev Mol Med) gives a different figure for a different group: up to 50% of white males are affected by 50 years of age. The two figures come from separate sources with different wording, so they are not combined here.
The usual pattern
According to MedlinePlus Genetics, men lose hair in a well-defined pattern that begins above both temples. Over time the hairline recedes to form a characteristic "M" shape. Hair also thins at the top of the head (vertex or crown), often progressing to partial or complete baldness.
A 2016 review of classification systems states that the Hamilton-Norwood system for males and the Ludwig system for females are the most commonly used to describe patterns of hair loss.
What drives it
A review published in 2002 states that the determining factors appear to be genetic predisposition coupled with the presence of sufficient circulating androgens.
On genes, the MedlinePlus Genetics page says scientific studies have confirmed only that variations in one gene, the AR gene, are involved. It also says the condition tends to cluster in families and that having a close relative with patterned hair loss appears to be a risk factor.
The prescribing information for Propecia (finasteride 1 mg) describes the scalp in men with male pattern hair loss. It states that the balding scalp contains miniaturized hair follicles and increased amounts of DHT compared with hairy scalp. It also describes Type II 5α-reductase as an intracellular enzyme that converts the androgen testosterone into DHT.
What else can cause hair loss, and how causes are found
| Question | What the source says |
|---|---|
| What other causes does MedlinePlus list? | The Hair Loss health topic says you can lose your hair if you have certain diseases such as thyroid problems, diabetes, or lupus, or with certain medicines or chemotherapy. It names stress, a low protein diet, a family history and poor nutrition as other causes. |
| How do reviews say the cause is found? | An American Family Physician review abstract states that a comprehensive history and physical examination, with targeted laboratory testing, may elucidate malnutrition, autoimmune diseases, and endocrine disease as causes of hair loss. |
| Is laboratory testing always needed? | A dermatology review abstract states that the first step is to obtain a good history and physical examination, that laboratory testing is often unnecessary, and that trichoscopy is fundamental for all hair diseases. |
These sources are general. They name causes without saying how common each one is, and they do not say which cause fits a given pattern of hair loss.
What this does not tell you
These pages describe male pattern hair loss in general. They do not diagnose any one person, and they do not say how fast or how far hair loss will go for any one man. The two prevalence figures above use different wording and groups, so they cannot be compared directly.
The MedlinePlus Genetics page says only variations in the AR gene have been confirmed, so these sources do not list other genetic causes. A licensed provider decides whether hair loss is male pattern hair loss or something else, and whether any treatment fits.