What If Your Scalp Were a Town? Understanding Androgenetic Alopecia Through a Different Lens

From the Hair Biology Essays

by Dr Gwen Adey

Hair biology is wonderfully complex. These essays explore the science behind hair growth and hair loss through observation, analogy and published research. They are for anyone who enjoys thinking not just about what happens, but why.

Hair loss is often explained using words such as miniaturisation, dihydrotestosterone (DHT) and follicular units. These are scientifically accurate terms, but they can be difficult to picture. If you’ve never looked at a hair follicle under a microscope, it isn’t always obvious what they really mean.

What if, instead, you imagined your scalp as a town?

Imagine a thriving town, filled with thousands of houses. Some are occupied by just one person, while others are home to an entire family. The town feels busy and full of life, not because it has more houses than anywhere else, but because so many of those houses are well occupied.

Now imagine that this town is your scalp.

Each house represents a follicular unit. Although many people think that each hair grows from a single follicle, most follicular units actually contain several individual follicles. Each follicle produces one hair, so houses with more residents produce more hairs. When viewed from a distance, the town appears full and healthy because so many houses are occupied by several active residents.

One of the most important things to understand about androgenetic alopecia is that the town usually doesn’t begin by losing its houses.

Instead, the houses gradually become less occupied. A follicular unit that once contained four healthy follicles may eventually have only three producing thick terminal hairs. Later it may produce only two, then one. The other follicles have not necessarily disappeared. Some remain in their homes, but they no longer contribute to the town in the way they once did. Instead of producing thick, healthy terminal hairs, they now produce only tiny, fine hairs that are barely visible.

In biological terms, this process is known as miniaturisation.

When you look in the mirror, you don’t see fewer houses. You simply notice that the town seems quieter than it once was.

This picture was inspired by a recent trichoscopy study, which found that during much of androgenetic alopecia the number of follicular units remains relatively stable while the number of terminal hairs emerging from each unit gradually declines.

In other words, the town often becomes quieter before it becomes smaller. 

Like any town, not every neighbourhood is the same. The follicles at the back and sides of the scalp inherited different biological instructions from those on the top. These instructions make them much more resistant to one of the environmental challenges affecting genetically susceptible follicles: dihydrotestosterone, or DHT. This is why the classic pattern of androgenetic alopecia usually affects the frontal scalp, mid-scalp and crown, while the occipital scalp often remains relatively full.

It is also why hair transplantation works.

Imagine, for a moment, that a removal lorry arrives in the occipital neighbourhood. The removal team carefully lifts a number of houses, complete with the residents inside, and transports them to a different part of the town.

Although the houses now stand in a new neighbourhood, the residents do not forget who they are. They bring their inherited biological instructions with them. The follicles continue to behave much as they did in their original location, remaining far more resistant to DHT than many of the follicles that originally occupied the recipient area. This phenomenon is known as donor dominance, and it is one of the reasons hair transplantation can produce long-lasting results in carefully selected patients.

Of course, no town is shaped by a single influence. DHT is an important part of the story, but it is not the whole story. The health of a follicle also depends on the environment in which it lives. Blood vessels deliver oxygen and nutrients, rather like roads bringing supplies into different neighbourhoods. Cells communicate with one another through complex chemical signals. Inflammation, ageing, hormones, genetics and many other biological processes all influence how well a follicle can continue to function over time. The availability of repair workers and materials also matters.

Perhaps future research will reveal even more about why some neighbourhoods remain healthy while others gradually decline. Every year, scientists uncover new signalling pathways, new cell types and new ways in which hair follicles communicate with their surroundings. The town, it seems, is far more complex than it first appears.

Hair biology is, of course, far more complicated than any analogy can fully capture. Every follicle is influenced by genetics, hormones, immune signals, ageing and countless other biological processes. Yet sometimes a simple picture can help us see more clearly.

The town analogy is my own way of visualising one element of androgenetic alopecia. It is not scientific terminology, but it is grounded in published research describing how hair follicles change as the condition progresses.

For me, imagining the scalp as a town does exactly that. It reminds me that androgenetic alopecia is rarely a story of houses suddenly disappearing. More often, it is the story of a town whose houses gradually become less occupied and whose busy streets slowly grow quieter.

Like so many of these essays, I have ended with more questions than answers.

Questions on my mind just now after considering this paper are:

Can we help follicles that are becoming less active become more active again? I.e. is it possible to help hair follicles miniaturising to optimise again? (I know some answers to this but I’d like to go deeper).

If so, how?

Can we learn from DHT resistant follicles at the back of the head what makes them relatively resistant to DHT so we can use whatever it is in therapeutics?

How long before the house is gone?

What is the window of opportunity for a particular “house” for us to intervene?

How can I use this town and houses analogy to explain how treatments like minoxidil work?

Anyway… leave these questions with me. I can’t promise answers, but I will think about the questions. And probably come up with some more questions!

References

1. Kim JH, et al. Trichoscopic features of androgenetic alopecia according to the basic and specific (BASP) classification: A retrospective observational study. Indian Journal of Dermatology, Venereology and Leprology. 2026.

Author: Dr Gwen Adey BDS MFDS RCS

First Published: 12/07/26