Male pattern hair loss has a recognizable shape, but other conditions can cause hair loss too. MedlinePlus says you can lose your hair if you have certain diseases, such as thyroid problems, diabetes, or lupus, or if you take certain medicines or have chemotherapy for cancer. It names stress, a low protein diet, a family history and poor nutrition as other causes. This guide sets out what the sources say about the usual pattern, the other causes they name and how reviews say clinicians tell them apart.
What pattern loss looks like
MedlinePlus Genetics says androgenetic alopecia is a common form of hair loss in both men and women, known in men as male pattern baldness. It says that in men, hair is lost in a well-defined pattern beginning above both temples, and 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 states that the Hamilton-Norwood classification system for males and the Ludwig system for females are most commonly used to describe patterns of hair loss. The Propecia label states that in men with male pattern hair loss the balding scalp contains miniaturized hair follicles and increased amounts of DHT compared with hairy scalp.
Age and how common it is
The MedlinePlus Genetics page says androgenetic alopecia can start as early as a person's teens and that more than 50 percent of men over age 50 have some degree of hair loss. A 2002 review states that up to 50% of white males are affected by 50 years of age. The two figures come from separate sources with different wording and groups, so they are not combined here.
Other causes the sources name
The MedlinePlus Hair Loss health topic names certain diseases (thyroid problems, diabetes, lupus), certain medicines, chemotherapy for cancer, stress, a low protein diet, a family history and poor nutrition. 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.
The passages used here name causes without saying how common each one is, and they do not describe how any one cause looks on the scalp.
How a clinician tells them apart
The American Family Physician abstract pairs a comprehensive history and physical examination with targeted laboratory testing. 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.
Both abstracts name the history and physical examination as part of the approach. They differ in emphasis on laboratory tests: one says targeted testing may help find causes, the other says testing is often unnecessary. Both are abstracts of reviews, so this guide reports only what they state.
What this does not tell you
This guide cannot tell a reader which cause applies. The sources describe a pattern, name causes and describe common approaches. They do not diagnose anyone, and the passages used here do not give how common each cause is. A licensed provider decides the diagnosis and which tests, if any, are needed.