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Thyroid Function and Vitamin D

Author: Christy Callahan, B.S. Biology

Thyroid Disorders
Recently, science has begun to investigate the potential link between vitamin D deficiency and impaired thyroid function. If thyroid hormone levels are imbalanced, or if the thyroid lacks nutrients to operate correctly, disorders can result. One common disorder is hypothyroidism. This disorder is characterized by low levels of active thyroid hormones, which can lead to weight gain, fatigue, poor sleep and sometimes depression. In contrast, hyperthyroidism is an excess of active thyroid hormones, which leads to weight loss and anxiety. Research is now indicating that low vitamin D may, in part, lead to hyperthyroidism.

Thyroid Gland
According to the University of Maryland Medical Center (UMMC), the thyroid gland is located on the front of the neck, just below the voice box. It is a wing-shaped gland, with one lobe on each side of the neck. The thyroid uses iodine to create its active hormones, T4 and T3, which are produced by follicular cells. These hormones work throughout the body, stimulating every tissue to make proteins and increase the amount of oxygen used by cells. Parafollicular cells in the thyroid produce a hormone called calcitonin, which works with the parathyroid hormone to regulate calcium levels in the body. Thyroid hormone secretions are controlled by the brain via the thyroid stimulating hormone, or TSH.

Vitamin D
Vitamin D can be obtained through certain foods, like eggs and fish, as well as through exposure to UV light. According to the Mayo Clinic, it is a fat-soluble vitamin that is needed for maintaining blood levels of calcium and phosphorus. It actually helps the body to absorb calcium; thereby playing a large role in bone and muscle health. Vitamin D may also play a role in immunity and potentially protect against disorders like cancer and autoimmune diseases.

According to a report in the October 2009 “Endocrinology,” vitamin D deficiency may influence thyroid function. The study states previous evidence had shown that vitamin D enhances regulatory T cells of the immune system. The study found that mice with vitamin D deficiency had lower T4 hormone levels and unexpectedly developed hyperthyroidism. Although this data shows a link between vitamin D and thyroid function, more research is needed.