Most of us have a small butterfly shaped gland in the front of our neck, just below the voice box. It’s part of our endocrine system. The endocrine system is a series of glands that produce the hormones required to regulate other body functions. Facing a stressful situation? Your adrenal gland swings into action and begins producing stress hormones like cortisol, adrenaline, and norepinephrine. These hormones are responsible for preparing the body for fight or flight. They ramp up cellular glucose metabolism to increase energy, speed up heart rate, sharpen mental alertness, dampen down pain responses and so on.

We also have hormones that regulate

  • the cellular uptake of various substances,
  • how fast chemical reactions happen in our body,
  • our metabolic functions.

Overall, our hormones control our growth and development, keep our internal body systems balanced, regulate our circadian clock, maintain good digestive health, and even assist with immune function.

In fact mammalian bodies are pretty remarkable! We have myriad processes that get switched on and off by the addition or subtraction of cofactor molecules. We have power generating structures in our cells (mitochondria) that turn glucose into the energy our cells need to do all the things they do.

Our cell membranes are full of different types of receptor molecules that bind with and ‘escort’ other molecules across the cell membrane where they can be utilised by the cell. Each of these receptors is coded to specific types of molecules. A thyroid receptor for example will only bind with thyroid hormone molecules. An insulin receptor will only bind with insulin molecules.

Even the amount of hormone circulating in the blood at any one time is kept within strictly regulated boundaries by a series of negative feedback loops.

How is this related to hair and hair loss?

The butterfly shaped gland in your neck that we mentioned at the start is your thyroid gland. It produces 3 types of hormones, 2 of which are relevant to hair growth. These 2 hormones are thyroxine (T4) and the more metabolically active triiodothyronine (T3). T3 is actively involved in every metabolic process that goes on in our body. From our gut health to the cellular metabolic processes that produce the energy our cells need to run – they all need thyroid hormone. In fact, every cell in our body has thyroid hormone receptors, which is a pretty clear indication that they all require thyroid hormone at some point to operate.

Your Cells, Energy, And Thyroid Hormone

Thyroid hormone stimulates several genes that produce proteins needed for cellular energy production. Some of these proteins are involved in transporting glucose across cell membranes (ie insulin). Glucose is the primary raw material used to generate cellular energy.   Others are involved in catalysing the process of converting glucose to ATP (cellular energy) within the mitochondria.   So thyroid hormone directly affects the amount of fuel supplied to the mitochondria as well as the process that starts the conversion of that fuel to energy. Thyroid hormone also stimulates mitochondriogenesis, which is the production of new mitochondria. More mitochondria equals more energy production.

When our thyroid hormone levels are right, and presuming we don’t have Type 2 hypothyroidism plus are eating properly, our cells are getting the nutrients and oxygen they require to run correctly. Energy production within the mitochondria is working as it should and we are replacing worn out mitochondria on a regular basis. We’re humming along nicely in fact. But….if our thyroid hormone levels get seriously out of whack, which happens when we develop an under active or overactive thyroid, it affects every part of us. Including our skin and hair.

Low Thyroid Hormones And Your Hair

At the base of each hair follicle is the dermal papilla. This is a bunch of living cells that produce new hair during the anagen, or active growth phase, of the hair cycle. They require nutrition and thyroid hormone like all our other cells. These are supplied via blood vessels in the skin.   When thyroid hormone levels drop (hypothyroidism) it impacts the amount of nutrients supplied to the dermal papilla cells. When this low thyroid hormone situation is temporary, there’s usually no harm done and hair growth remains unaffected. However, when hypothyroidism remains undetected and / or untreated, it will affect your hair growth. In fact, hair and skin are always among the first things affected by ongoing hypothyroidism – hair loss and dry skin are very early symptoms of the disorder.

Why Is This So?

We’ve already mentioned what a marvellous creation the body is. Another manifestation of this is the way it can prioritise body systems in order of importance when it comes to survival. When supplies of nutrients run short, existing supplies are redirected to those organs essential for survival – heart, lungs, brain, circulatory system, liver, kidney etc. Alas, important though skin is, it’s nevertheless towards the bottom of the list. Hair, being completely non-essential for survival, is even lower! They are therefore the first things to get cut back when supplies run low.

When blood supply to skin tissue and hair follicles is decreased it reduces the nutrients, oxygen and thyroid hormone they get. This in turn directly affects cellular metabolism in the follicles and dermal papilla.   Eventually, in someone with ongoing hypothyroidism, they simply can’t support new hair growth any more. Therefore, as hairs enter the telogen stage and fall out they’re not replaced. Or the new hairs are thin and weak. It can also shock existing hair into premature telogen (telogen effluvium).

Hypothyroidism Associated Hair Loss

Hypothyroidism associated hair loss is usually diffuse. It manifests more as an overall thinning of hair rather than patchy hair loss. It’s also typically reversible once hormone treatment is started, and maintained. It generally takes several months for hair regrowth to become noticeable so it’s important to be patient. New hair regrowth may also be a different colour and texture to existing hair too.

Unfortunately levothyroxine, the drug most commonly used for treating hypothyroidism has also been linked with hair loss.

Hashimoto’s Thyroiditis, Autoimmune Diseases And Hair Loss

The most common cause of hypothyroidism in developed countries is the autoimmune disease Hashimoto’s Thyroiditis.   Autoimmune diseases love company and often hunt in packs. If you have one, you’re far more susceptible to developing another one.

There are a couple of types of hair loss associated with autoimmune diseases. Some forms of Lupus can invade the scalp, causing hair loss and scarring which permanently kills the follicles. Alopecia areata is an autoimmune disease in which hair follicles are attacked by the body’s own immune system, causing bald patches.   However, it is more typically associated with an over active thyroid (hyperthyroidism). Hair loss is also far more aggressive and often appears in circular patches as opposed to the more diffuse thinning caused by thyroid problems.

Whilst thyroid problems like hyperthyroidism and hypothyroidism predominantly affect women, men are by no means immune. Therefore, if you notice that your hair is beginning to look a bit thin overall, and is not its normal healthy looking self, it would pay to talk to your doctor about possible thyroid problems. Particularly if you’re also experiencing a few other early symptoms of low thyroid activity such as depression, dry skin, brittle cracking nails, cold sensitivity, unexplained weight gain and brachycardia (slow heart rate).

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