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Word Cloud on a white background - Vitamin D

Vitamin D Deficiency and Thyroid Health: What’s the Link?

The perils of vitamin D deficiency are well documented, and symptoms such as fatigue, flu, dizziness, hair loss and even weight gain have been either conclusively proven or strongly implicated.

Dr. Theodore C. Friedman, M.D., Ph.D. is not alone in pointing out the strong association between hypothyroidism and vitamin D deficiency. In a paper on the subject, Dr. Friedman explains that “both vitamin D and the thyroid hormone bind to similar receptors called steroid hormone receptors.

"A different gene in the vitamin D receptor was shown to predispose people to autoimmune thyroid disease including Graves’ disease and Hashimoto’s thyroiditis.”

In this article, we’ll examine the links between vitamin D deficiency and thyroid disease, and suggest means of upping your vitamin D to protect your health.

Vitamin D and Thyroid Health: What the Studies Say

It is worthwhile looking at some of the studies which have been conducted to assess the links between serum vitamin D levels and thyroid function.

In one oft-cited 2011 study72% of individuals with autoimmune thyroid disease were shown to be deficient in vitamin D. This compared to 31% of healthy individuals.

In other words, a person with autoimmune thyroid disease was more than twice as likely to be deficient in vitamin D. What’s more, vitamin D deficiency was shown to correlate with the presence of anti-thyroid antibodies.

In and of itself, this was an interesting study which did not reach firm conclusions. However, in the paper’s final passage the researchers made some interesting remarks.

“Deficiency of vitamin D was linked to the presence of antithyroid antibodies and abnormal thyroid functions… as treatment with vitamin D is inexpensive and carries minimal side effects, vitamin D supplements may be recommended for autoimmune thyroid disease patients.”

In 2016, another study investigating the relationship between vitamin D and thyroid autoimmunity, subjects with hypothyroidism were compelled to consume vitamin D supplements for a period of 12 weeks. Afterwards, demonstrable improvements in blood levels of thyroid-stimulating hormone were recorded.

Another randomised, double-blind, placebo-controlled trial (2018) sought to further evaluate the effect of supplementation on thyroid function among 201 hypothyroid patients aged 20-60. Patients were randomly assigned into two groups, to take either a weekly dose of 50,000 IU or a placebo. The trial ran for 12 weeks, with markers related with thyroid function assessed before and after the intervention.

The study was a major success, with supplements improving “serum TSH (thyroid-stimulating hormone) and calcium concentrations compared with placebo”.

What scientists are still trying to determine is whether vitamin D deficiency influences the pathogenesis of hypothyroidism, or is itself a consequence of the condition. In either case, rectifying low vitamin D levels is advisable.


Clearly one’s vitamin D intake correlates to some degree with the state of one’s thyroid, and having your levels checked periodically – and supplementing where necessary – is prudent.

It is also important to consider your iodine intake, since this trace mineral is actually required by the body to make thyroid hormones. You can find out more by reading this article.

The importance of vitamin D for thyroid health will surely continue to be highlighted, and we intend to keep pace with the research by continually updating this very blog to reflect new developments.