The science behind hair growth, shedding and why some follicles gradually become thinner

Most of us don't think about our hair follicles very often.

You wash your hair, style it and get on with your day.

But underneath the surface, every individual hair is going through a continuous biological cycle.

It grows.

It rests.

It eventually falls out.

And then the cycle starts again.

So why does hair loss happen?

And why do some men gradually develop a receding hairline or thinning crown while others maintain their hair for decades?

The answer starts with understanding the hair growth cycle.

The Hair Growth Cycle

Every hair on your scalp goes through different stages.

The three main phases are:

Anagen — the growth phase

Catagen — the transition phase

Telogen — the resting phase

These phases don't happen to every hair at exactly the same time.

That's why you don't normally lose all of your hair at once.

Instead, individual follicles move through their own cycles independently.

1. Anagen — The Growth Phase

Anagen is the active growth phase of the hair cycle.

During this stage, cells within the hair follicle are actively dividing and producing a hair shaft.

For scalp hair, the anagen phase can last for several years.

The longer a follicle remains in anagen, the longer the hair can potentially grow.

Most of the hairs on your scalp are normally in this growth phase at any given time.

2. Catagen — The Transition Phase

Catagen is a much shorter transitional stage.

The follicle stops actively producing a growing hair and begins to shrink.

This phase typically lasts only a few weeks.

Think of it as the follicle preparing to move from active growth into its resting phase.

3. Telogen — The Resting Phase

During telogen, the follicle is essentially resting.

The old hair remains attached for a period of time before eventually being shed.

A new growth cycle can then begin.

This means that seeing a hair in your shower doesn't necessarily mean something is wrong.

Hair shedding is a normal part of the hair cycle.

The important question is whether the amount and pattern of shedding are changing.

Why Do We Lose Hair Every Day?

It can be alarming to see hairs on your pillow, clothes or in the shower.

But some daily shedding is completely normal.

Because different follicles are at different stages of the hair cycle, some hairs naturally reach the end of their cycle and fall out while other follicles are actively producing new hairs.

The result is a continuous process of growth and shedding.

This is very different from progressive hair loss.

So What Happens With Male Pattern Hair Loss?

Male pattern hair loss, also known as androgenetic alopecia, is different.

In genetically susceptible follicles, hormones and genetics can cause the follicles to gradually become smaller.

This process is called miniaturisation.

Instead of producing a thick terminal hair, an affected follicle may progressively produce finer, shorter hairs.

Over time, the hair becomes less visible.

Eventually, some follicles may produce very little visible hair.

What Is DHT?

One of the key hormones involved in male pattern hair loss is dihydrotestosterone (DHT).

DHT is produced when testosterone is converted by an enzyme called 5-alpha reductase.

In genetically susceptible individuals, DHT can contribute to the miniaturisation of certain hair follicles.

Importantly, not every follicle responds to DHT in the same way.

This helps explain why male pattern hair loss tends to affect particular areas.

The hairline and crown can become thinner while other areas of the scalp remain relatively unaffected.

Why Does Hair Become Thinner Before It Disappears?

This is an important part of understanding hair loss.

A follicle doesn't necessarily go from producing a thick hair to producing nothing overnight.

The process can be gradual.

A simplified example might look like:

Thick hair

↓

Slightly finer hair

↓

Shorter, finer hair

↓

Very fine, less visible hair

This gradual process is known as miniaturisation.

It can make the overall density of your hair appear to decrease even before you develop obvious bald areas.

Why Does Hair Loss Take Years?

Male pattern hair loss is usually progressive rather than sudden.

The rate varies considerably between individuals.

Some men may notice significant changes over a relatively short period.

Others may experience very gradual thinning over many years.

There isn't one universal timeline.

Genetics, age and individual follicle sensitivity all contribute to how the condition develops.

This is one reason why comparing your hair to someone else's isn't particularly useful.

Your hair-loss journey can be completely different from theirs.

Why Does Treatment Take So Long?

Understanding the hair cycle also helps explain why hair-loss treatments don't produce overnight results.

Hair grows relatively slowly.

And follicles need time to move through their biological cycles.

Even when a treatment is having an effect, you may not immediately see a dramatic difference in the mirror.

This is why hair-loss treatments generally need to be used consistently for several months before their effectiveness can be properly assessed.

It also explains why taking photographs over time can be more useful than checking your hair every day.

What Is Hair Shedding?

Hair shedding simply refers to hairs leaving the scalp.

Some shedding is normal.

However, certain conditions can cause a significant increase in shedding.

One example is telogen effluvium, which can occur after certain physical or psychological stresses such as illness, major stress, significant weight loss or other physiological changes.

Unlike male pattern hair loss, telogen effluvium often causes more diffuse shedding across the scalp.

The two conditions can also occur together.

If you experience sudden or significant shedding, it's worth discussing it with a healthcare professional rather than assuming the cause.

Shedding vs Hair Loss

These terms are often used interchangeably, but they aren't necessarily the same thing.

Hair shedding describes the process of hairs falling out.

Hair loss generally refers to a reduction in hair density or the failure of hair to regrow normally.

You can therefore experience noticeable shedding without developing permanent hair loss.

Likewise, male pattern hair loss can progress gradually without dramatic shedding.

This is why simply counting the number of hairs you see in the shower isn't a reliable way to monitor male pattern hair loss.

Why Your Hairline and Crown Can Be Affected Differently

Male pattern hair loss doesn't necessarily affect the entire scalp equally.

Certain follicles are genetically more susceptible to the effects of DHT.

This creates the familiar patterns associated with male pattern hair loss:

• Recession around the temples
• A changing frontal hairline
• Thinning at the crown
• Gradual reduction in overall density

Meanwhile, follicles in other areas can remain relatively resistant.

This difference in follicle sensitivity is one of the reasons hair loss often follows recognisable patterns.

Can You Stop the Hair Growth Cycle?

No — and you wouldn't want to.

The hair cycle is completely normal.

The goal of hair-loss treatment isn't to stop hair from shedding altogether.

Instead, when treating male pattern hair loss, the objective is generally to slow the underlying miniaturisation process and/or support hair growth, depending on the treatment.

This distinction is important.

Seeing a few hairs fall out doesn't automatically mean your treatment has stopped working.

Why Consistency Matters

Hair-loss treatment is often a long-term process.

Because follicles operate through slow biological cycles, consistency is important.

Stopping and starting treatments repeatedly makes it much harder to assess whether a treatment is working.

It's also important to understand that established treatments for male pattern hair loss generally need to be continued to maintain their benefits.

For more information about individual treatments, see our guides to:

5% Minoxidil

and

Finasteride

What Can You Do If You're Worried About Hair Loss?

The first step isn't necessarily buying a treatment.

It's understanding what's happening.

Try taking consistent photographs of:

Front

Both temples

Top

Crown

Use similar lighting, distance and hairstyle each time.

Then compare photographs over several months.

This can provide a much more objective picture than checking your hair in the mirror every day.

When Should You Seek Professional Advice?

It's worth seeking medical advice if you're concerned about progressive hair loss or if the pattern isn't typical of male pattern hair loss.

In particular, sudden or patchy hair loss, significant scalp inflammation, pain, or other unusual symptoms may have causes that require investigation.

A qualified healthcare professional can assess your symptoms and determine whether further investigation or treatment is appropriate.

The Bigger Picture

Hair loss isn't simply a matter of "losing hairs."

It's a biological process involving:

Genetics

↓

Hormones

↓

Hair follicles

↓

The hair growth cycle

↓

Changes in follicle size and hair production

Understanding this process makes it much easier to understand why hair loss develops gradually, why treatments take time and why not every type of shedding means the same thing.

Key Takeaways

Hair growth is cyclical.

Every follicle moves through growth, transition and resting phases.

Some shedding is normal.

Seeing hairs in the shower doesn't automatically mean you're losing your hair.

Male pattern hair loss is different.

Genetics and hormones can cause susceptible follicles to gradually miniaturise.

Hair can become finer before it becomes invisible.

This gradual process explains why thinning can be difficult to notice at first.

Treatment takes time.

Hair follicles operate on slow biological cycles, so results shouldn't be judged from day-to-day changes.

Understanding the cause matters.

Different types of hair loss require different approaches.

The Thrive Journal

At Thrive, we believe education comes before treatment.

Hair loss can be confusing, especially when you're confronted with conflicting advice, miracle products and unrealistic promises.

The Thrive Journal exists to make the science behind hair loss and treatment easier to understand.

Explore our other guides:

The Complete Guide to 5% Minoxidil (2026)

The Complete Guide to Finasteride (2026)

Should You Add Tretinoin to Minoxidil?

The Complete Guide to Male Pattern Hair Loss (2026)

More guides coming soon.