evidence: The thyroid is a small, butterfly-shaped gland in the front of your neck. In people with Hashimoto’s disease - the immune system makes antibodies that attack the thyroid gland - large numbers of white blood cells, which are part of the immune system, build up in the thyroid - the thyroid becomes damaged and can’t make enough thyroid hormones [...] Hashimoto’s disease causes your thyroid to become damaged. Most people with Hashimoto’s disease develop hypothyroidism. Rarely, early in the course of the disease, thyroid damage may lead to the release of too much thyroid hormone into your blood, causing symptoms of hyperthyroidism.3 [...] Researchers are looking at other ways in which diet and supplements—such as vitamin D and selenium—may affect Hashimoto’s disease.2 However, no specific guidance is currently available.3