Thyroid and Hair Loss: What Your Hair Is Trying to Tell You

Your hair might be the first sign something is off with your thyroid.

The thyroid is a small gland in your neck that regulates your metabolism, energy, and a surprising number of other body functions — including your hair growth cycle. When it's not working properly, your hair often shows it before anything else does.

Thyroid-related hair loss is more common than most people realise, and it's frequently missed because the hair symptoms look similar to other types of shedding. If you're trying to understand all the possible causes, our Complete Guide to Hair Loss in South Africa covers every major trigger in one place.

How does the thyroid affect hair?

Thyroid hormones (T3 and T4) play a direct role in regulating the hair growth cycle. They influence how long follicles stay in the active growth phase and how quickly they cycle through rest and shedding.

When thyroid hormone levels are too low (hypothyroidism) or too high (hyperthyroidism), this cycle gets disrupted — pushing more follicles into the resting and shedding phase than normal.

Hypothyroidism and hair loss

Hypothyroidism (underactive thyroid) is the more common cause of thyroid-related hair loss. The thyroid isn't producing enough hormone, which slows down many body processes — including hair growth.

Signs of hypothyroidism beyond hair loss include:

• Fatigue and sluggishness, even with enough sleep
• Weight gain without changes to diet
• Feeling cold all the time
• Dry skin and brittle nails
• Brain fog and difficulty concentrating
• Constipation
• Depression or low mood
• Slow heart rate

The hair loss pattern is typically diffuse — thinning across the whole scalp rather than in patches. A distinctive sign of hypothyroidism is thinning of the outer third of the eyebrows, though this isn't present in everyone.

Hyperthyroidism and hair loss

Hyperthyroidism (overactive thyroid) can also cause hair loss, though it's less common. When the thyroid produces too much hormone, it speeds up the hair cycle — causing follicles to cycle through growth and shedding too quickly.

Signs of hyperthyroidism include:

• Unexplained weight loss
• Rapid or irregular heartbeat
• Feeling hot and sweating excessively
• Anxiety, irritability, or tremors
• Difficulty sleeping
• Increased appetite

Hashimoto's thyroiditis

Hashimoto's is an autoimmune condition where the immune system attacks the thyroid, gradually causing it to underfunction. It's the most common cause of hypothyroidism and is significantly more prevalent in women. Hair loss is a common symptom, and it can occur even when thyroid levels appear borderline rather than clearly abnormal.

What tests should you ask for?

A standard TSH (thyroid stimulating hormone) test is the usual starting point. However, TSH alone doesn't always give the full picture. Ask your GP for:

• TSH — the standard screening test
• Free T3 and Free T4 — the active thyroid hormones
• Thyroid antibodies (TPO and TgAb) — to check for Hashimoto's

Some people have "subclinical" thyroid dysfunction — where TSH is borderline but T3/T4 or antibodies indicate a problem. This can still cause hair loss even when a basic test comes back "normal".

What's the treatment?

Thyroid-related hair loss is treated by addressing the thyroid condition itself — not just the hair. This typically means:

• Hypothyroidism: Thyroid hormone replacement medication (levothyroxine), prescribed by your doctor
• Hyperthyroidism: Medication to reduce thyroid hormone production, radioactive iodine therapy, or surgery in some cases
• Hashimoto's: Hormone replacement plus monitoring; some people also benefit from dietary changes

Once thyroid levels are stabilised, hair shedding typically slows within 1–3 months. Visible regrowth takes longer — usually 6–12 months.

Supporting your hair during recovery

While your thyroid levels are being treated, you can support your scalp and follicles with:

• A gentle, sulphate-free shampoo with scalp-supportive ingredients
• A targeted hair growth serum with peptides or rosemary oil to stimulate follicle activity
• Adequate protein and iron in your diet — both commonly low in people with thyroid issues

Our recommendation at Partners Hair

If you suspect your hair loss might be thyroid-related, start with a blood test. Once you have a diagnosis and treatment plan, our team can help you build a hair care routine that supports recovery. Book a scalp consultation at your nearest Partners Hair salon or shop our hair loss range online.

Frequently Asked Questions

Can thyroid problems cause hair loss?

Yes — both an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism) can disrupt the hair growth cycle and cause diffuse shedding across the scalp.

Will my hair grow back after treating my thyroid?

In most cases, yes. Once thyroid hormone levels are stabilised with treatment, shedding slows and hair regrows — though it can take 6–12 months to see full recovery.

What does thyroid hair loss look like?

It typically presents as diffuse thinning across the whole scalp rather than patchy loss. Thinning of the outer eyebrows is a classic sign of hypothyroidism, though not everyone experiences this.

Can I have thyroid-related hair loss with a normal TSH?

Yes. Subclinical thyroid dysfunction — where TSH is borderline and Free T3/T4 or antibodies are abnormal — can still cause hair loss. Ask for a full thyroid panel, not just TSH.

Where can I find hair loss treatment products in South Africa?

Partners Hair stocks professional-grade scalp and hair growth products available online and in our salons across South Africa. A scalp consultation can help identify the right routine for your recovery.