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Vitamin D linked to thyroid health

Hashimoto’s disease is an autoimmune condition that causes low thyroid function and symptoms of hypothyroidism. A blood test can diagnose this condition by measuring anti-TPO antibodies. These antibodies damage the enzymes involved in thyroid hormone production, causing typical low thyroid symptoms.

As with many autoimmune conditions, lifestyle factors, foods and nutrients can play a role in the triggering the disease. In patients with Hashimoto’s disease, vitamin D deficiency is quite common, but it’s not clear if it’s the cause or effect of the disease. More research is needed to explore this connection, especially since vitamin D deficiency is quite prevalent.

One study that explored the relationship of vitamin D to Hashimotos’s was done in Greece in 2015. The researcher looked at vitamin D levels in 218 euthyroid (normal thyroid) Hashimoto’s Disease patients (mostly women, average age 35). They found that a whopping 86%, or 186 of the 218 patients, were low in vitamin D (< 20 ng/mL). All of the patients were positive for anti-TPO antibodies to confirm their diagnosis of Hashimoto’s. An interesting observance was that the greater the D3 deficiency, the higher the anti-TPO levels were. Could this be a link to a causal effect for vitamin D? To explore how restoring proper vitamin D levels would affect the disease, patients took 1200- 4000 IU vitamin D3 daily for four months. The goal (which all patients achieved) was to increase D levels to a minimum of 40 ng/mL.

It was found that vitamin D3 did indeed lower anti-TPO levels after four months. By this time, the anti-TPO levels decreased significantly (about 20%).

This small study seems to suggest that low vitamin D levels may predispose a person to developing Hashimoto’s disease and higher anti-TPO levels. It also suggests that restoring vitamin D levels to “normal” can help reduce anti-TPO antibodies levels. (Note: the exact number that represents “normal” vitamin D is still controversial and some physicians believe it should be much higher than tests currently state).

This short study only lasted four months, so it would have been interesting to see if longer term vitamin D3 supplementation further reduced anti-TPO antibodies. Considering that this study was conducted in sunny Greece, it was surprising that so many of the patients were low in vitamin D, despite reporting plenty of daily sun exposure. Maybe this indicates that some people have a problem with converting sunshine to vitamin D, but scientists haven’t yet identified the reasons why.

The take home message is that if you have Hashimoto’s disease, be sure to get your vitamin D levels checked, even if you live in a sunny place and think deficiency is unlikely. If your level is low, aim to increase it to at least the highest end of “normal” on the test, not just the low or middle. Be sure to take a good multivitamin with plenty of D3, A, K2 (e.g. MK-4, MK-7), selenium, and iodine. Also investigate if you have potential food allergies (gluten being quite common) which cause a lot of inflammation and can worsen autoimmune flare ups.

Hell J Nucl Med 2015; 18(3): 222-227

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