Thyroid Hormone and Your Hair

It’s one of the first things that many women check when they start to experience hair loss: their thyroid. So, what could explain hair loss (and other symptoms of hypothyroid) when thyroid labs come back as “normal” or when you’re already on thyroid hormone medication?


First, let me just emphasize how important your thyroid is to having healthy hair! The hair growth process is very energy demanding. It relies on fully functioning mitochondria (those little powerhouses in our cells), which in turn depend on fully functioning thyroid hormone.

Before we dig into how the thyroid works, let me ask you something. How many of these classic examples of hypothyroid symptoms can you identify with?

  • thinning hair
  • fatigue or being tired a lot
  • cold hands and feet
  • unintentional weight gain
  • weight loss resistance
  • constipation or stools that are hard to pass
  • low or depressed mood
  • dry skin
  • dandruff
  • low libido
  • high cholesterol


Why would someone with “normal” thyroid labs be experiencing hypothyroid symptoms like these?


I’d be remiss if I didn’t point out the elephant in the room. TSH (thyroid stimulating hormone) alone is not an adequate assessment of thyroid health. Read more about why that is in this article.


Let’s start at square one and make sure you know how your thyroid gland and its hormones function.


So, things actually start with the hypothalamus. This is a gland in our brain and it responds to the levels of thyroid hormones in the body and releases its hormone called TRH (thyrotropin releasing hormone). That hormone (TRH) then stimulates another gland called the pituitary. The pituitary releases its hormone called thyroid stimulating hormone (TSH). It’s the TSH hormone that acts on the thyroid gland and stimulates it to produce thyroxine (called T4) and triiodothyronine (called T3).


In summary: hypothalamus (TRH) -> pituitary (TSH) -> thyroid (T4, T3)


When thinking about the connection between our hair health and our thyroid health the important thing to note is that it’s the activated thyroid hormone (T3) that’s needed. Our thyroid’s produce a lot more of the T4 than the T3. It’s up to special enzymes called deiodinases convert T4 to the activated T3.


(P.S. There is more than one type of deiodinase enzyme and they have different functions. For the sake of simplicity, I’m just going to refer to deiodinases in this general manner rather than D1, D2, D3).


For women who are experiencing hair loss and also suspect hypothyroid its important to investigate (1) if the thyroid gland is functioning optimally to produce adequate thyroid hormone, and (2) if the T4 is being properly converted to T3.


1.) The thyroid gland isn’t functioning optimally

Common reasons the thyroid gland isn’t outputting enough thyroid hormone is nutritional deficiencies (more on this below) or damage to the thyroid gland (for example, in the case of Hashimotos thyroiditis).


When thinking about the connection between our hair health and our thyroid health the important thing to note is that it’s the activated thyroid hormone (T3) that’s needed


2.) T4 isn’t being adequately converted to T3

What if you have adequate T4 (either from the thyroid gland or from thyroid hormone medication) BUT you’re still experiencing hypothyroid symptoms like hair loss? It could be that T4 isn’t being converted to T3. This is also called peripheral hypothyroid, because generally your thyroid gland itself is outputting hormone, but the peripheral conversion of T4 to T3 is falling behind.


What are some potential reasons that could be happening?

  • Poor Nutrient Status

Nutrients like selenium, iodine, iron, and the amino acid tyrosine are needed by deiodinases to convert T4 to T3 (they’re also important to produce adequate thyroid hormone in the first place). Before rushing to supplement with any of these it’s important to determine individual need (and iodine can actually make autoimmunity worse for people with Hashimotos) and also consider why the deficiency came about in the first place.

  • Chronic Inflammation

When you see increasing levels of reverse T3 (rT3), it can be a sign that there is some unaddressed inflammation present. Reverse T3 is an inactive form of thyroid hormone that your body may resort to producing as a way to protect your cells from further inflammatory damage. What could be causing inflammation? There are so many possible root causes of inflammation, but they could include gut infections, viruses, mold toxicity, insulin or leptin resistance, immune dysregulation, or chronic stress.

Ready to start digging in to the root causes of your inflammation?

  • Undereating + Overtraining

Undereating and overtraining should be seen as a combination of poor nutrient status and chronic inflammation, but I wanted to call it out specifically because I think it’s too often overlooked. It’s also something I see quite frequently in the women I work with. Not eating enough for our energy needs and working out too strenuously can cause low nutrients, but it also provokes inflammation and puts stress on our body.


Ok, what if your thyroid tests all come back “normal” but you’re still experiencing hypothyroid symptoms? This could be related to something called cellular hypothyroidism which is a term being used to describe inadequate levels of T3 reaching the thyroid hormone receptors in the cell. The reasons for this can be complex, but more often than not it comes down to the chronic inflammation we were just talking about above.


Is poor thyroid function an issue for your hair? Take my quiz to learn your hair loss type!


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