Vitamin D Deficiency and Thyroid Relationship

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The thyroid is connected with the development and building function of the human body. Without this important gland, the body would have trouble regulating all the important connections inside each human cavity. Furthermore, a person’s health would struggle to exist without the thyroid gland. The thyroid gland sits just under the Adam’s Apple, and is in charge of jump starting hormones that regulate body temperature, growth within the body, blood pressure, and how quickly or slowly metabolism functions.

Vitamin D is a substance that comes mainly from sunlight and many dairy products. This vitamin helps keep bones strong throughout the lifetime of an individual. But, if there is not enough Vitamin D within the body, deficiencies may occur. Vitamin D deficiencies may stem from a few factors. People who do not get enough sunlight lose the great abilities the sun gives the human body. Also, people may have a Vitamin D deficiency because of an allergy to milk or from people who keep strict vegan habits. Some of the health risks that could come from Vitamin D deficiencies include cardiovascular disease, cancer, asthma in children under the age of 18, and cognitive issues in elderly adults, like dementia and Alzheimer’s Disease.

The truth is the thyroid and Vitamin D deficiency share more in common than most think. There are correlations between the thyroid and Vitamin D that could show patients and doctors warning signs within the human body. Without enough Vitamin D or too much of the vitamin, the thyroid could have prolonged issues.

Vitamin D Linked to Thyroid Health

Articles seem to come out daily on Vitamin D and its health benefits to the body. Even more articles from the media and medical journals warn about the lack of Vitamin D and the detrimental effects it could have on the body. Many of the Vitamin D deficiencies connect with a plethora of autoimmune diseases. These diseases include balancing issues between Th1, Th2, and Th3 cells within the body. When there is enough Vitamin D in the body, the vitamin does a great job regulating these cells. Th1 cells are mediated cells, while Th2 are the immune system’s humoral arms, and Th3 (or T-regulatory cells) oversee the differentiation between Th1 and Th2 cells. But, when there is not enough Vitamin D, the cells have trouble being guided through communication of the vitamin.

A Vitamin D deficiency, within the body, may lead to an autoimmune thyroid disease or AITD. AITD is know more commonly as Hashimoto’s thyroiditis or autoimmune thyroiditis. A Vitamin D deficiency also could play a role in an autoimmune-mediated thyroid dysfunction, where the Th1 cells become unbalanced in the body. With these diseases, the body begins to attack its own thyroid gland. The gland will become inflamed and the thyroid will continue to decrease hormone production over time. Heredity is usually associated with an AITD, but a deficiency in Vitamin D could also be the culprit. Women are usually affected more than men, and an AITD affects people between 40 to 60 years of age more often than not. Some of the symptoms of an inflamed thyroid may include weight gain, missed menstrual cycles in women, dry skin, fatigue, the loss of hair, and stiffness of joints, among other things. More serious symptoms may include depression and swelling of the face tissue.

Not Enough Vitamin D

A study done at the University of California – Los Angeles (UCLA) was created to see if low Vitamin D in an individual would make AITD worse. The researchers at UCLA believed there was a “dampening effect” on the response of the immune system all over the body’s connective synapses. Also, they thought the thyroid might be involved in this worsening as well. Ultimately, the research was proven wrong, but something else was found in the process, connecting with Vitamin D and the thyroid.

In this experiment, the researchers used two different mice groups. One group had Vitamin D given with their food, and the other group of mice did not get the same vitamin. Even before much experimentation was done, researchers found that the mice without Vitamin D in their diet had levels of T4, or thyroxine, below normal. In turn, these mice were already prone to hypothyroidism.

As the experiment continued, the mice without Vitamin D showed a slower response from the immune system, which the researchers expected, but the thyroid in each mouse could not handle the stresses of these tests. This made mice without Vitamin D more prone to injuries leading to hyperthyroidism, on top of the issues already found.

Even though this study was not done on humans particularly, but rather mice, its research findings are very important moving forward with the connection of the thyroid and Vitamin D. The findings proved two things. First, without Vitamin D, a low-functioning thyroid could be a possibility, and, secondly, the thyroid may continue to have issues if Vitamin D is not in a normal human diet. The thyroid has always had irritants from the environment, like fluoride and perchlorate. Usually, Vitamin D helps keep these irritants at bay, but without the vitamin, the irritants continue to harm the body’s thyroid. Some researchers believe this might be why patients notice weight gain because of the metabolism slowing, specifically in the winter season.

Vitamin D Overload

When patients hear they have a Vitamin D deficiency, which may result in an autoimmune disease, many believe they just need a ton of sunlight or a huge amount from a Vitamin D supplement to fix the problem with their thyroid. However, this could not be further from the truth. The thyroid issue can’t be fixed that easily, and something more might be going on in the body. For example, a Vitamin D issue may be because of poor absorption in the body’s cells. An inflamed GI tract is very common in people who find out their thyroid is functioning less than normal. When the GI tract is swollen, Vitamin D can’t be immersed in the areas of the body that needs its nutrients. On the other hand, it could also just be due to the fact that you are not getting enough sunlight and Vitamin D.

For Vitamin D to perform in the body appropriately, the Vitamin D receptor, or the VDR, must be activated. A lot of times, an autoimmune disease can stymie this process. When the VDR does not function, the Vitamin D in the body is reduced, hindering its uses. When patients have an AITD, many have an issue with their VDR or what doctors refer to as VDR polymorphisms. To simplify this terminology, even if Vitamin D blood levels are normal in the body, a person may be experiencing a Vitamin D deficiency because of a thyroid with low functionality.

Increase the Vitamin D

When it comes to someone with an autoimmune thyroid disease, patients will need to up their dose of Vitamin D over time to help with the deficiency. Some studies have suggested Vitamin D supplements of 35 ng/mL are adequate for most people dealing with an autoimmune thyroid disease. However, other doctors state that more Vitamin D, such as 50 ng/mL, may be needed to help some patients. Still, the American Journal of Clinical Nutrition agrees that no more than 35 ng/mL should be used by patients when taking Vitamin D.

As stated earlier, higher is not better with Vitamin D necessarily. The American Journal of Medicine proved bone density stayed the same when 32 ng/mL of Vitamin D was taken, but when the amount was raised to over 45 ng/mL, bone density started to shrink in size, leading to bone structure issues like fractures and breaks. Also, the European Journal of Epidemiology observed that patients who took levels of Vitamin D exceeding 89 ng/mL had heart attacks at a level three times greater than patients that took less Vitamin D into the body.


The thyroid and Vitamin D have a direct correlation with each other, when it comes to the human cells of the body. When Vitamin D lacks within the body, hypothyroidism could occur. Also, if the body continues to have a deficiency of Vitamin D, hyperthyroidism could be a result. A large increase of Vitamin D is not the answer to thyroid issues. When a massive increase of ng/mL happens in the body, many life-threaten issues could be conceivable. An average amount of Vitamin D should be taken when thyroid issues occur, instead of a major increase of the vitamin. A thyroid supplement that gives you the recommended daily value taken over a couple weeks seems to be the ideal solution. Changing your diet may also help.

  1. Reply
    Iva October 3, 2018 at 11:48 am

    How can a person activate VDR? How can VDR polymorphisms be treated (naturally)?

  2. Reply
    John April 19, 2018 at 5:41 pm

    What do these supplemental values mean for Vitamin D dose? Correlation to an OTC supplement of 5,000 IU?

    • Reply
      Thyroid Advisor April 19, 2018 at 7:49 pm

      Hi John,

      Here is a rough estimate for someone would weighs 150lbs.

      To achieve this level… Take this much supplement per day…
      20 ng/ml………………..1000 IU
      30 ng/ml………………..2200 IU
      40 ng/ml………………..3600 IU
      50 ng/ml………………..5300 IU
      60 ng/ml………………..7400 IU
      70 ng/ml………………..10100 IU

      • Reply
        John April 19, 2018 at 8:08 pm

        Thank you! I was taking OTC Vitamin D at 1,000 Iu, then at 5,000 Iu daily.
        Now I am on an Rx for a “Chole” / capsule taken 1 x week at a 50,000 units dose. It is good to know I was not taking anywhere close to the ng/ml dosage equivalent!!! I am 230# and will attempt calculating this later.

  3. Reply
    Mary September 6, 2017 at 11:08 am

    It should be mentioned that iodine also has key role in thyroid, and environmental impact from pollutants, like floride and chrorine block iodine absorbing and have a negative impact on thyroid also foods like broccoli and crociferris vegetables bind to block iodine from absorption

    • Reply
      Thyroid Advisor September 27, 2017 at 2:50 am

      Hi Mary,

      Yes. Our article on Iodine talks about that.

      • Reply
        stacey July 26, 2020 at 8:51 pm

        Does anyone know how much vitamin K2 needs to be taken in respect to Vitamin D3 (like if a person takes 50,000 iu of D3)?

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