Male pattern hair loss, known clinically as androgenetic alopecia, is the most common cause of hair loss in men, and its biology is better understood than almost any other aspect of hair. The central player is dihydrotestosterone, or DHT, a hormone the body produces from testosterone using an enzyme called 5-alpha-reductase.
Miniaturization, step by step
In a DHT-sensitive follicle, each successive hair cycle is a little shorter and the hair produced a little finer, until over years the follicle yields only short, wispy hairs, and eventually may stop producing visible hair at all. Crucially, the follicle does not die suddenly — it shrinks progressively. This is why the timing of treatment matters so much: a miniaturized but still active follicle can often be coaxed back toward fuller growth.
Evidence Check: The DHT model is well established. Genetics determine susceptibility, while treatments work by blocking DHT or stimulating follicles directly.
Why the pattern is a pattern
Hair recedes at the temples and thins at the crown, while the hair around the back and sides of the head typically persists for life. This map reflects the differing DHT sensitivity of follicles in different regions, which is genetically determined. The follicles at the back and sides are largely resistant to DHT — which is precisely why they are the donor source for hair transplantation.
Separating real causes from folklore
- Wearing hats does not cause pattern baldness.
- Frequent shampooing removes loose hairs that were already shedding — it does not cause loss.
- Poor scalp circulation is not the driver.
- Stress can trigger a different, usually temporary form of shedding, but is not the cause of genetic pattern baldness.
Why early action changes the outcome
The progressive, partly reversible nature of miniaturization has a direct practical consequence: the best time to act is early, when follicles are shrinking but still active. The proven treatments are far better at preserving and partially reviving struggling follicles than at resurrecting ones that have been dormant for years.
When hair loss signals something else
Sudden loss, patchy bald spots, loss accompanied by redness, scaling, or pain, or shedding that affects the whole scalp evenly can signal other conditions — from thyroid disease to nutritional deficiency to autoimmune alopecia. These warrant a medical evaluation rather than an over-the-counter remedy.
Disclaimer: Sudden, patchy, or rapid hair loss can signal other medical conditions. See a doctor for an accurate diagnosis.