Thyroid Hair Loss: Symptoms, Causes and Is It Reversible?
Thyroid-related hair loss happens when an underactive or overactive thyroid disrupts the hormones your hair cycle depends on, causing thinning across the whole scalp rather than patches. The most important things to know: it often goes unrecognised as the cause, it needs a simple blood test to diagnose, and, best of all, it is usually reversible once the thyroid condition is treated. Here is how to recognise it and what to do.
Key takeaways
- Both an underactive (hypothyroid) and overactive (hyperthyroid) thyroid can cause hair loss.
- It shows as diffuse thinning across the whole scalp, not bald patches.
- A simple GP blood test can diagnose a thyroid condition.
- With the right treatment, thyroid-related hair loss is usually reversible.
- Regrowth takes months, so patience and gentle hair care are part of the journey.
What is your thyroid and what does it do?
The thyroid is a small, butterfly-shaped gland at the front of your neck, and it is your body's metabolic thermostat: it regulates metabolism, energy, digestion and heart rate through the hormones it releases. Those same hormones influence your hair follicles, which is why a thyroid that is running too slow or too fast so often shows up in your hair.
Thyroid function can be affected by autoimmune conditions, genetics, medication, pregnancy and the menopause, among other factors.
How does a thyroid problem cause hair loss?
Hair follicles are sensitive to hormone levels. When thyroid hormones are out of balance for a sustained period, the hair cycle slows and more follicles sit in the resting phase, so hair gradually becomes thinner across the whole scalp. Unlike alopecia areata, which causes distinct patches, thyroid hair loss is a general reduction in volume and density, and it can also make hair feel dry, brittle and slower to grow. In some people the outer third of the eyebrows thins too.
What are the symptoms of a thyroid condition?
The two most common thyroid disorders are an overactive thyroid (hyperthyroidism, including Graves' disease) and an underactive thyroid (hypothyroidism, including Hashimoto's). Hair loss can appear with either.
| Overactive thyroid (hyper) | Underactive thyroid (hypo) |
|---|---|
| Weight loss despite normal eating | Weight gain |
| Rapid heartbeat, palpitations | Slower pulse |
| Nervousness, anxiety, insomnia | Lethargy, low mood |
| Increased sweating, heat intolerance | Feeling cold, dry skin |
| More frequent bowel movements | Constipation, hoarse voice |
| Hair thinning | Hair thinning |
If several of these sound familiar alongside your hair changes, that pattern is well worth mentioning to your GP.
How is thyroid hair loss diagnosed and treated?
Diagnosis is straightforward: a GP blood test measures your thyroid hormone levels (TSH, and often T4). If a condition is found, your doctor or an endocrinologist will prescribe treatment, commonly levothyroxine for an underactive thyroid, or antithyroid medication for an overactive one, and monitor your levels until they are stable.
Is thyroid-related hair loss reversible?
Usually, yes, and this is the reassuring part. Once your thyroid levels are back in a healthy range, the hair cycle typically returns to normal and density gradually recovers. Because hair grows around a centimetre a month, expect the visible recovery to take several months rather than weeks, and remember the tip above: do not be alarmed if shedding seems to continue early in treatment while the old cycle works itself through.
How can you support your hair in the meantime?
Medical treatment does the real work, but gentle care helps your hair look its best while it recovers:
- Handle gently: soft brushing, no tight styles, minimal heat, thinner hair is more delicate.
- Wash kindly: a gentle, sulphate-free shampoo such as our Grow Me shampoo cleanses without stripping and supports the look of fuller hair, cosmetic support, not a treatment.
- Eat well: a balanced diet with enough protein, iron and zinc supports normal hair, and your GP can check for any deficiencies at the same blood draw.
- Be patient and kind to yourself: hair recovery follows hormone recovery, a few months behind.
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Frequently asked questions
Can thyroid problems cause hair loss?
Yes. Both an underactive and an overactive thyroid can cause diffuse thinning across the whole scalp by disrupting the hormones the hair cycle depends on.
What does thyroid hair loss look like?
A general reduction in volume and density all over, rather than distinct bald patches. Hair may also feel dry and brittle, and the outer eyebrows can thin.
Is thyroid hair loss reversible?
Usually yes. Once the thyroid condition is treated and hormone levels stabilise, hair typically regrows over several months.
Can thyroid medication cause hair loss?
Some shedding early in treatment is usually the original condition working through the long hair cycle rather than the medication. If you are concerned, talk to your doctor rather than stopping medication.
How do I find out if my thyroid is behind my hair loss?
Ask your GP for a thyroid blood test. It is quick and can also check related things like iron levels.
How long does hair take to grow back after thyroid treatment?
Expect gradual improvement over several months once your levels are stable, as hair grows roughly a centimetre a month.
Do any products treat thyroid hair loss?
No. Only treating the thyroid condition addresses the cause. Gentle, supportive hair care simply helps your hair look its best during recovery.
Thyroid-related hair loss is one of the most treatable kinds there is: diagnose it with a simple blood test, treat the condition, and let your hair follow your hormones back to normal. If your shedding is diffuse and unexplained, put a GP visit at the top of your list. For related reading, see what causes telogen effluvium and menopause and hair loss.
