Vitamin D and Thyroid Health: Is there a Link? (SQ-78)

Vitamin D is on a roll these days. We have long known that the sunshine vitamin is critical for bone and muscle health. Ongoing research reveals that vitamin D may also support a wide array of functions and have health benefits that go beyond this classic role in bone development. For example, it is known to regulate immunity, support heart functions and reduce inflammation. Recently, a lot of studies have come out suggesting that vitamin D may help lower the risk of upper respiratory infections, asthma and allergies in both adults and children.

Did you know vitamin D is an important player in your thyroid health too? Well, it shouldn’t come as a surprise. People with thyroid disorders, even those on medications require additional nutritional support to improve their symptoms. And vitamin D is an important part of this nutritional mix, that also includes the likes of iodine, selenium, zinc, magnesium, B12 and probiotics to name a few.

Vitamin D is required for optimal thyroid function and studies show that people with thyroid issues have low vitamin D status. [1] In addition, vitamin D deficiency is also known to increase the risk of auto immune thyroid disorders such as Hashimoto’s disease, Grave’s disease and post-partum thyroiditis. So, what is the link between vitamin D and thyroid health? How does the sunshine vitamin fit into this equation?

Thyroid gland, its hormones and the work they do

The thyroid gland is a small butterfly shaped gland in the front of your neck, just below the Adam’s apple.  It produces thyroid hormones – thyroxine (T4) and triiodothyronine (T3) – that are in charge of regulating many critical functions in the body. It regulates breathing rate, metabolism and weight management, heart rate, growth and development, reproductive functions, menstrual cycle and even cholesterol levels are all regulated by thyroid hormones T4 and T3.

Every cell in your body relies on thyroid hormones to work properly. The pituitary gland secretes thyroid stimulating hormone (TSH), which signals the thyroid gland to produce T4 and T3. Most of the hormone produced in this process is T4, which is not active and mostly functions as a pro-hormone. T4 is converted into T3, which is the active form.

The thing is, your thyroid gland is extremely sensitive to all kinds of internal and external disturbances which can interfere with the normal functioning of the thyroid gland, leading to either hyperthyroidism or hypothyroidism.

Hyperthyroidism is a condition where your thyroid gland overworks and makes more thyroid hormones than what your body needs.

Hypothyroidism is a condition where the thyroid gland underworks and doesn’t make sufficient amounts of thyroid hormones.

Thyroid problems and the autoimmune element

A healthy immune system protects the body from invading pathogens such as bacteria, viruses, fungi, and parasites. It releases special proteins called antibodies that identify and destroy foreign invaders. But in some people, the workings of the immune system go haywire. It mistakes the body’s own healthy tissues for foreign tissue, and starts attacking them, creating inflammation and damage in the tissue. When this auto-immunity is directed at the thyroid gland, it results in autoimmune thyroid disorders.

Hashimoto’s disease is the most common cause of hypothyroidism (underactive thyroid) in people.  It is an autoimmune disorder where the immune system creates TPO antibodies that attack the cells of the thyroid gland. This causes inflammation and impairs the ability of the thyroid gland to produce thyroid hormones, leading to hypothyroidism. In some very rare cases, Hashimoto’s may also cause symptoms of hyperthyroidism.

Graves’ disease is the most common underlying cause of hyperthyroidism (overactive thyroid). It is an autoimmune disorder where your immune system creates specific antibodies called thyroid-stimulating immunoglobulins (TSIs). And as the name suggests, these antibodies stimulate your thyroid gland to grow and produce too much thyroid hormone.

What makes your immune system go faulty in the first place? There is no clear scientific explanation on why this really happens. But scientists believe that genetics play a determining role in whether you will develop autoimmune conditions, including autoimmune thyroid disorder. Environmental triggers also make you highly susceptible – such as poor gut health, adrenal dysfunction, chronic stress, metabolic disorder, food sensitivities (gluten intolerance), hidden or persistent infections, chronic inflammation, imbalances in blood sugar levels and exposure to environmental toxins. If you already have a pre-existing auto immune condition, this also increases your risk of autoimmune thyroid disorders.

Nutritional deficiencies are yet another piece of the thyroid puzzle. Sadly, this component is often overlooked by most mainstream doctors. The fact is nutrients like selenium, vitamin D, zinc, vitamin A, vitamin C and magnesium all play a crucial role in the production, conversion and activation of the thyroid hormones. If your body is lacking in any of these nutrients, it impairs your thyroid function and health.

Vitamin D and thyroid health

Vitamin D helps in healthy thyroid functions

Nearly all the cells in your body have vitamin D receptors (VDR). These include immune cells and cells in your brain, heart, lungs, muscles, thyroid gland and intestines. The active vitamin D binds with these receptors on cells all over the body and activate them. The activated receptors, in turn, regulate the expression of genes that are involved in carrying out various functions and processes that make your body run the way it should.   

As an example, let’s see what happens when vitamin D binds to receptors of the immune cells? It turns on genes involved in the production of anti-bacterial proteins, which helps the body to fight a range of infections. And when it binds with receptors in the intestines, it turns on the genes that help in calcium absorption. This is how vitamin D basically works in the body, wearing many hats and performing all kinds of functions required for maintaining overall health. Your thyroid gland also contains receptors for vitamin D, thus playing an important role in healthy thyroid function.

A 2017 study concluded that “Overall, the results of the current study suggest that for normal thyroid function an optimal 25(OH)D concentration above 100–125 nmol/L may be required. Although improving other nutrient status, like vitamin B12, should also be taken into consideration. Of concern, recommended daily intakes for vitamin D are aimed at achieving serum 25(OH)D concentrations of 50 nmol/L and targeted at bone health alone. Vitamin D offers a safe and economical approach to improve thyroid function and may provide protection from developing thyroid disease.” [2] The study also found that higher levels of serum vitamin D reduced the symptoms of low thyroid function; for example, brain fog, weight gain, mood issues, poor sleep and low energy levels.

Vitamin D and risk of autoimmune disorders

There is plenty of evidence that associates low levels of vitamin D with an increased risk of autoimmune disease – including multiple sclerosis, type 1 diabetes, lupus, rheumatoid arthritis and thyroid disease such as Hashimoto’s and Grave’s disease.

This 2017 review of the available data on vitamin D and thyroid health found that vitamin D deficiency may be associated with an increased risk of thyroid autoimmunity. [3]

Vitamin D plays a dual role when it comes to immune system functions. It strengthens the natural immune system, which helps in fighting infections. But it also regulates the adaptive immune system, that improves immune tolerance and helps reduce the risk of developing autoimmunity. How does it work?

There are many types of T cells, including T helper cells, Cytotoxic T Cells, Memory T Cells, Natural Killer cells, all with different functions. These also include T regulatory cells (Tregs) that help build immune tolerance and supress immune response to self-antigens, thus preventing the development of autoimmune diseases. Studies show that people with autoimmune diseases may have dysfunction or depletion of Treg cells. [4] It is believed that vitamin D improves the functions of T regulatory cells. [5]

Does vitamin D deficiency increase the risk of thyroid problems?

Studies show that low Vitamin D levels are associated with:  

- The development of autoimmune thyroid diseases (AITDs) such as Hashimoto's thyroiditis (HT) and Graves' disease (GD). [6] [7]
- Higher risk of thyroid antibodies [8]
- Lower levels of thyroid-stimulating hormone (TSH)
- Risk of autoimmune thyroid disorder in pre-menopausal women. [9]

Can Vitamin D Supplementation help manage thyroid disorders?

Studies show that vitamin D supplementation improves thyroid function. Healthy levels of vitamin D works by:

1. Reducing levels of circulating TSH [10]
2. Reducing the levels of thyroid antibodies [11] [12]
3. Preventing inflammation

There is another interesting element involved here. Let’s take a scenario where your thyroid gland may be making enough T4 and T3 hormones. But this T3 works inside the cells and it first needs to bind to the T3 receptors present in the nucleus of every cell. This is when T3 gets activated and become useful to the cells. And you need vitamin D (and also vitamin A) to carry out this critical step. In fact, deficiency in vitamin D may be the reason why your thyroid treatment is not giving you the desired results.

References:

1. Wang et al. Meta-analysis of the association between vitamin D and autoimmune thyroid disease. Nutrients. 2015
2. Mirhosseini et al. Physiological serum 25-hydroxyvitamin D concentrations are associated with improved thyroid function—observations from a community-based program. Endocrine. 2017
3. Nettore et al. Sunshine vitamin and thyroid. Rev Endocr Metab Disord. 2017
4. Bossowski et al. Analysis of chosen polymorphisms in FoxP3 gene in children and adolescents with autoimmune thyroid diseases. Autoimmunity. 2014 Sep; 47(6):395-400.
5. Siklar et al. Regulatory T Cells and Vitamin D Status in Children with Chronic Autoimmune Thyroiditis. J Clin Res Pediatr Endocrinol. 2016
6. Tamer et al. Relative vitamin D insufficiency in Hashimoto's thyroiditis. Thyroid. 2011
7. Mazokopakis et al.  Is vitamin D related to pathogenesis and treatment of Hashimoto's thyroiditis? Hell J Nucl Med. 2015
8. Sayki et al. Isolated Vitamin D Deficiency Is Not Associated with Nonthyroidal Illness Syndrome, but with Thyroid Autoimmunity. The Scientific World Journal. 2015.
9. Choi et al. Low levels of serum vitamin D3 are associated with autoimmune thyroid disease in pre-menopausal women. Thyroid. 2014
10. Chailurkit et al. High vitamin D status in younger individuals is associated with low circulating thyrotropin. Thyroid J. 2013
11. Chaudhary et al. Vitamin D supplementation reduces thyroid peroxidase antibody levels in patients with autoimmune thyroid disease: An open-labeled randomized controlled trial. Indian J Endocrinol Metab. 2016
12. Simsek et al. Effects of Vitamin D treatment on thyroid autoimmunity. J Res Med Sci 2016

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