Thyroid Problems & Hair Loss: Is There a Connection?

Yes. Both an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism) are recognised causes of hair thinning and excessive shedding.
​

Thyroid hormones help regulate many of the body’s essential functions, including metabolism, energy levels, and the hair growth cycle. When thyroid hormone levels become too high or too low, normal hair growth can be disrupted.
​

Hair loss linked to thyroid disease is usually diffuse, meaning it affects the entire scalp rather than one specific area. Many people notice increased shedding, reduced hair density, or changes in hair texture before realising an underlying thyroid condition could be contributing.
​

The good news is that thyroid-related hair loss is often reversible once the underlying condition is identified and treated.
​

The thyroid is a small butterfly-shaped gland located at the front of the neck.
​

It produces two key hormones:

These hormones influence how cells throughout the body function, including the cells within hair follicles.
​

When thyroid hormone levels fall outside their normal range, the hair growth cycle can become disrupted.
​

Hair follicles are highly active structures that rely on the right balance of hormones to grow normally.
​

Thyroid hormones help regulate:

When thyroid hormone levels become imbalanced, more hairs can enter the resting phase of the hair growth cycle. This can lead to increased shedding and slower regrowth.
​

Yes.
​

Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) can disrupt the hair growth cycle.
​

Hypothyroidism
​

Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormone.
​

Common symptoms include:

Hair changes may include:

Hypothyroidism is one of the most common endocrine conditions associated with hair loss.
​

Hyperthyroidism
​

Hyperthyroidism occurs when the thyroid produces too much thyroid hormone.
​

Common symptoms include:

Hair changes may include:

Although the underlying causes are different, both underactive and overactive thyroid conditions can disrupt the normal hair growth cycle.
​

Unlike male or female pattern hair loss, thyroid-related hair loss typically presents as diffuse shedding across the scalp.
​

Common signs include:

Some people with hypothyroidism also notice thinning of the outer third of their eyebrows, which is a recognised feature of an underactive thyroid.
​

Because these symptoms overlap with other types of hair loss, thyroid disease can sometimes go unrecognised as an underlying cause.
​

This is one of the most common areas of confusion.
​

Thyroid Hair Loss

Female Pattern Hair Loss

To learn more about the differences, read: What Is Female Pattern Hair Loss? A Simple Explanation.
​

Yes, many people with thyroid disease develop a form of shedding called telogen effluvium.
​

Telogen effluvium occurs when more hairs than usual enter the resting (telogen) phase of the hair growth cycle before being shed several weeks or months later.
​

This is the reason thyroid-related hair loss often appears several months after hormone levels first become abnormal.
​

To learn more about different types of hair loss, read: What Are the Most Common Types of Hair Loss? A Simple Explanation.
​

If a thyroid condition is suspected, a healthcare professional may recommend blood tests.
​

Common tests include:

Because thyroid problems can sometimes present primarily as hair loss, testing may be appropriate even if symptoms seem mild.
​

When investigating persistent hair shedding, it’s important to look beyond the scalp. Hair loss can sometimes be a sign of an underlying health condition rather than a problem with the hair itself.
​

This is why understanding internal health factors is so important. Related reading: Can Low Iron Cause Hair Loss? A Simple Explanation.
​

In many cases, yes.
​

Once thyroid hormone levels return to a healthy range, many people notice:

However, regrowth takes time.
​

Hair follicles don't respond immediately to changes in hormone levels. It's common for improvement to take several months after thyroid function has stabilised.
​

Most people notice:

Patience is important. Hair grows slowly, and recovery is usually gradual.

If a thyroid disorder is the main cause of hair shedding, addressing the thyroid condition itself is usually the first priority.
​

However, it’s possible to have more than one cause of hair loss at the same time.

For example:

In these situations, treating the underlying thyroid condition may just be one part of your treatment plan.
​

If another type of hair loss is also contributing, prescription treatments remain the gold-standard option for male and female pattern hair loss because they work directly at the hair follicle.
​

To learn more, read: What Actually Treats Hair Loss? The Evidence-Based Ingredients Explained.
​

It may be worth speaking to a healthcare professional if:

Simple blood tests can often provide valuable answers.
​

Thyroid disorders are a recognised cause of hair loss and thinning.

Both underactive and overactive thyroid conditions can disrupt the hair growth cycle, leading to increased shedding and reduced density.
​

The good news is that thyroid-related hair loss is often reversible once the underlying condition is identified and appropriately treated.
​

Understanding the connection between thyroid health and hair growth is an important part of investigating persistent hair loss. Sometimes the answer isn’t just on your scalp – it’s what’s happening inside your body.
​