HORMONES AND THE HAIR CYCLE

Hair loss and thyroid problems

Thyroid hormones affect many processes in the body, including the hair cycle. Both an underactive and an overactive thyroid may be associated with diffuse hair loss.

In brief

Thyroid problems can cause diffuse hair loss or a change in hair texture.
Other symptoms, such as fatigue, weight changes or heart palpitations, may provide clues but are not conclusive.
Diagnosis is based on medical assessment and blood values such as TSH and free T4.
Hair recovery usually follows later than improvement in other symptoms because the hair cycle needs time.

THYROID HORMONES

How does the thyroid affect the hair cycle?

Thyroid hormones help regulate the metabolism and growth of many cells in the body. A disruption can cause more hairs to enter the resting phase at the same time.

As a result, diffuse shedding may develop several weeks to months later. The hair may feel less dense across the entire scalp without clearly defined bald patches.

UNDERACTIVE THYROID

Hair loss with hypothyroidism

An underactive thyroid may cause fatigue, sensitivity to cold, weight gain, dry skin and slower thinking. The hair may become drier or thinner.

The combination and severity of symptoms differ between individuals. Blood testing is needed to establish whether the thyroid is genuinely underactive.

OVERACTIVE THYROID

Hair loss with hyperthyroidism

An overactive thyroid may cause weight loss, heat intolerance, restlessness, trembling or heart palpitations. Diffuse hair loss may also occur.

These symptoms require medical assessment. There are various possible causes, and the cause determines the appropriate treatment.

This can lead to telogen effluvium, a form of diffuse hair loss in which more hairs than usual enter the resting phase at the same time.

BLOOD TESTING

How is a thyroid problem investigated?

A doctor assesses your symptoms, medication and medical history and may request blood tests. TSH and free T4 provide information about thyroid function.

An abnormal value must be interpreted in context. A single symptom or result does not always tell the full story.

RECOVERY

When does the hair recover?

After appropriate treatment, hair loss may gradually decrease, but the hair cycle lags behind the recovery of hormone levels. Visible improvement often takes several months.

If the hair continues to thin, another cause may also be involved, such as androgenetic alopecia, a nutritional deficiency or medication.

Important to know

Hair loss alone is not enough to diagnose a thyroid problem. Have your symptoms assessed and never adjust thyroid medication on your own. Sudden, localised or inflamed hair loss may have another cause.

Frequently asked questions about hair loss and thyroid problems

Yes, an underactive thyroid can be associated with diffuse hair loss and dry or brittle hair. Testing is needed to establish the cause.

An overactive thyroid can also disrupt the hair cycle and cause diffuse shedding.

TSH and free T4 are often assessed. Any additional tests depend on the individual situation.

Recovery is often possible after thyroid function has stabilised, but visible improvement usually takes months.

Hair loss may be related to the condition, changes in hormone levels or sometimes the medication. Discuss this with your healthcare professional and do not change anything on your own.

Assessment is advisable when persistent hair loss occurs alongside clear weight changes, heart palpitations, extreme fatigue or other symptoms.

MAP YOUR HAIR LOSS

Which pattern do you recognise?

The TRIX Hair Check helps you distinguish between several common patterns. A possible thyroid disorder can only be assessed professionally and with blood tests.

Start the Hair Check Read about telogen effluvium