Hair Falling Out With Hypothyroidism? What Your Thyroid Is Telling You

The short answer: If your hair is thinning or falling out and you have hypothyroidism or Hashimoto's, your thyroid is usually only part of the reason. Low thyroid hormone slows your hair growth cycle, but the hair loss often continues because of low iron, low protein, low zinc or vitamin D, an autoimmune flare, stress, or shifting hormones. Each one needs a different approach, so test first instead of guessing.

Shedding a little hair every day is normal. Finding clumps in the shower, a wider part, a thinner ponytail, or losing the outer third of your eyebrows is not. That pattern is a clue.

How your thyroid affects your hair

Every hair on your head goes through a growth phase, a resting phase and a shedding phase. Your thyroid hormone helps set the pace of that cycle. Hair follicles are some of the fastest-dividing cells in your body, so they need a steady supply of thyroid hormone, energy and nutrients.

When your thyroid is low, more of your hair moves out of the growth phase and into the resting phase at the same time. A few months later, that hair sheds. This is why hair loss often shows up two to four months after the thing that caused it. It is also why your hair usually thins evenly across your whole scalp instead of in one patch.

Hair that is dry, coarse and breaks easily, along with thinning eyebrows, dry skin and brittle nails, points to your thyroid. You can read more about how I look at thyroid health on the thyroid page.

Why your hair can keep falling out even when your labs look "fine"

You may be told your thyroid is under control while your hair keeps falling out. There are a few reasons this happens.

• Your TSH is in range, but your active thyroid hormone is low. TSH alone does not show how much active hormone your cells are getting. Free T3 is the hormone your hair follicles actually use. I go deeper in my article on normal TSH with hypothyroid symptoms.
• Your body is not converting T4 into T3 well. Low selenium, low zinc, low iron, stress and inflammation all slow that conversion.
• Your immune system is still attacking your thyroid. With Hashimoto's, high thyroid antibodies can mean ongoing inflammation even when your other numbers look normal.
• Something else is driving the hair loss. Your thyroid may be stable, but a nutrient gap or hormone shift is still pulling your hair out of its growth phase.

1. You are low in iron

This is the most common missing piece I see with thyroid hair loss. Your hair follicles need iron to grow. Your thyroid also needs iron to make its hormone. When iron is low, both suffer.

The key number is ferritin, which shows your iron stores. A "normal" ferritin result can still be too low for healthy hair growth. Heavy periods, a mostly plant-based diet, low stomach acid and gut issues all make low iron more likely.

Do not start iron without testing. Too much iron is a problem too, so check your levels first.

2. You are not getting enough protein

Your hair is made of protein. If you do not eat enough of it, your body uses what you do eat for more important jobs first. Your hair is last in line.

Build each meal around a good source of protein, such as eggs, fish, poultry, meat or legumes. Low stomach acid, which is common with hypothyroidism, can also make it harder to break down and absorb the protein you eat.

3. You are low in zinc, selenium or vitamin D

Your thyroid and your hair share many of the same nutrient needs.

• Zinc supports hair follicle repair and helps convert T4 into active T3.
• Selenium helps convert thyroid hormone and protects your thyroid.
• Vitamin D supports your immune system and your hair follicles. Low vitamin D is common with Hashimoto's.

More is not better with these nutrients. Too much selenium, for example, can cause hair loss on its own. Test, then replace what you are missing. You can read more in my post on beneficial supplements for an under-active thyroid.

4. Your immune system is still active

If you have Hashimoto's, your immune system is attacking your thyroid. That ongoing inflammation can affect your hair in two ways. It lowers your thyroid output, and it raises your risk of other autoimmune hair loss, which shows up as round, smooth patches.

Look at what keeps your immune system activated: gut issues, food sensitivities, mold, heavy metals and dental infections are all common triggers. Read more in the many dental triggers of Hashimoto's.

5. Stress, illness or a big change

A high fever, surgery, a crash diet, rapid weight loss, giving birth or a period of intense stress can push a large amount of hair into the resting phase at once. You will see the shedding two to four months later.

A change in your thyroid medication dose can also cause temporary shedding while your body adjusts. Do not stop or change your medication on your own. Any change should happen only with your prescribing practitioner's supervision.

6. Your hormones are shifting

If you are in your late 30s, 40s or 50s, shifting hormones in perimenopause and menopause can thin your hair on top of a thyroid problem. A higher Testos-to-Estros balance can also thin the hair on your scalp while increasing hair on your chin and face. This is common with PCOS.

If your hair loss came along with changes to your cycle, mood, sleep or skin, test your hormones along with your thyroid.

Test first, then act

There are too many possible causes to sort out hair loss by trial and error. Iron will not help if your zinc is the problem, and more thyroid support will not help if your ferritin is low.

The labs I use most often for thyroid hair loss are:

• A full thyroid panel: TSH, free T4, free T3, reverse T3, and TPO and thyroglobulin antibodies.
• An iron panel with ferritin.
• A nutrient panel for zinc, selenium, vitamin D and B12.
• A hormone panel if you are in perimenopause or menopause, or your cycle has changed.
• A hair tissue mineral analysis to see your mineral balance and any heavy metal burden.

You can see the panels and order them on the labs page.

How I approach thyroid hair loss

I work from two questions: what is your body missing, and what is it carrying that it should not be? Hair loss with hypothyroidism usually involves both. A deficiency, such as low iron or low zinc, leaves your follicles without what they need to grow. A burden, such as heavy metals, mold or chronic inflammation, keeps your thyroid and immune system under strain.

The order matters. First, replace what your labs show you are missing and eat enough protein. Then calm your immune system and support your thyroid. Then remove what is interfering. Doing these in the right order keeps you from feeling worse along the way.

Be patient with your hair. It grows slowly, so it often takes three to six months after you address the cause to see new growth come in.

When to see your medical provider

Talk to your medical provider promptly if your hair loss is sudden and severe, comes out in round patches, comes with a red, scaly or painful scalp, or comes with extreme fatigue, a racing heart, unexplained weight changes or very heavy periods. These need medical evaluation first.

Find out why your hair is falling out

You do not have to accept thinning hair as part of having a thyroid condition. Start by finding out what your hair is missing.

Not sure where to start? Take the free quiz. It takes a few minutes and shows you which area to look at first: thyroid, gut, hormones, energy, skin or sleep and stress.

If you would rather talk it through, book a free 15-minute call. We will go over your symptoms and the labs that make sense for you.