Androgenetic Alopecia

Androgenetic alopecia is the clinical name for male and female pattern hair loss: the gradual, genetically determined shrinking of scalp follicles under the influence of [DHT](/glossary/dht).

Where you'll meet it

On every consultation note and every prescription, sometimes shortened to AGA. It is the diagnosis behind the large majority of hair loss in men, more than nine in ten cases by most estimates, and a large share in women. When a clinic talks about hair loss without naming a cause, this is the one it means.

What is actually happening?

Androgenetic alopecia is follicles shrinking rather than hair falling out. Susceptible follicles respond to DHT by miniaturising, producing progressively finer, shorter, lighter hairs over successive growth cycles until what they make is no longer visible. Under magnification, a thinning area shows a mix of thick and thin hairs side by side, and that variation is what a dermatologist is looking for when they diagnose it.

Which follicles are susceptible is set genetically. In men the pattern follows a recognisable shape, recession at the temples and thinning at the crown that meet over time, described by the Norwood scale. The horseshoe at the back and sides is generally not susceptible, and that resistance is the entire basis of transplant surgery: hair moved from there keeps its resistance wherever it is planted.

How do you know it is this and not something else?

Mostly by the pattern and the pace. Androgenetic loss is gradual, symmetrical and patterned, usually with a family history behind it. Other kinds look different and are treated differently. Telogen effluvium is diffuse shedding across the whole scalp a few months after a stressor, and it usually recovers. Alopecia areata comes as smooth, round patches and is autoimmune. Scarring alopecias come with itching, soreness, redness or scaling, destroy the follicle permanently and need a dermatologist quickly.

If your loss is sudden, patchy, diffuse rather than patterned, or uncomfortable, see a doctor before you buy anything. Two kinds can also overlap: someone with pattern loss can have a bout of shedding on top of it, which is one reason a diagnosis from someone who has actually looked at your scalp is worth having.

Does it ever stop?

It slows, but it rarely stops on its own. Pattern loss is progressive across decades, at a pace that varies a great deal between people and tends to be faster when it starts young. That is why the stage you are at today matters less than the stage you are heading for, and why surgeons are wary of operating on a pattern that has not finished declaring itself.

What treats it?

Finasteride addresses the cause by lowering DHT, and minoxidil prolongs the growth phase of the follicles you still have. Both are treatments for androgenetic loss specifically, and both work for as long as you take them. A transplant redistributes resistant hair into the thinning area but does nothing to the condition itself, which carries on in the hair around the grafts.

Using any of these on a different kind of loss wastes time that a correct diagnosis would have saved. Start Here sets out the order I would work through it in.

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