Are Vitamin D Deficiency & Hypothyroidism Related?

Hypothyroidism is a metabolic disorder where the thyroid gland does not make enough thyroid hormone. Vitamin D is both a vitamin and a hormone that serves several functions in the body, but is primarily responsible for depositing calcium into the bones. People with hypothyroidism may have low serum vitamin D levels and there is some concern as to whether a vitamin D deficiency and hypothyroidism are related.

Hypothyroidism

The thyroid produces two hormones, thyroxine or T4 and triiodothynine or T3. A deficiency of either of these hormones causes your metabolism to slow. Hypothyroidism is caused by several factors including damage to the thyroid from medications or autoimmune disorders, and a lack of thyroid stimulating hormone, or TSH. Hypothyroidism affects the entire body and patients can experience symptoms in all systems of the body. Some of the most common symptoms include sensitivity to cold, depression, fatigue and rapid weight gain.

Vitamin D

You get vitamin D in fortified foods, such as milk, and you also synthesize vitamin D, in the form of the hormone cholecalciferol, in your body with exposure to sunlight. A severe vitamin D deficiency causes a condition called rickets, or soft, weak bones. People who live in areas that get less sunlight, such as the Northern Hemisphere, are at high risk for low vitamin D levels. People with darker skin are also more vulnerable because dark skin does not absorb sunlight as easily.

Vitamin D and Hypothyroidism

Hypothyroidism has several secondary effects which may also be affected by vitamin D deficiencies. Advanced hypothyroidism may cause hypertension and high blood sugar. People with low levels of vitamin D are also more susceptible to these disorders, according to the University of Maryland Medical Center. Weight gain and obesity are a component of hypothyroidism, and people with lower levels of vitamin D are more likely to be obese than individuals with higher levels of vitamin D. Hypothyroidism causes depression and Tatiana Cannell, M.D., of VitaminDCouncil.com, indicates that hypothyroidism patients taking 4,000 IU of vitamin D per day showed an improvement in mood.

Conclusion

While there appears to be a correlation between Vitamin D and hypothyroidism, the nature of the relationship is unclear. Two studies published in PubMed, one comparing the effects of Vitamin D deficiency on autoimmune disease of the thyroid and another on vitamin D levels in individuals with thyroid nodules or tumors both report low vitamin D and in individuals with impaired thyroid function. It is unclear, however, if the impaired thyroid function caused the vitamin D deficiency, if the reverse is true, or if a third, undiscovered factor contributes to both conditions.