Problems with the thyroid can be caused by:
Iodine deficiency: Iodine deficiency is a lack of the trace elementiodine, an essential nutrient in the diet. It may result in a goiter, sometimes as an endemic goiter as well as cretinism due to untreated congenital hypothyroidism, which results in developmental delays and other health problems.
Autoimmune diseases: in which your immune system attacks your own body, leading either to hyperthyroidism (caused by Graves’ disease) or hypothyroidism (caused by Hashimoto’s thyroiditis)
Nodules, or non-cancerous lumps, inside the thyroid : thyroid nodules are malignant, ultrasound determination that a nodule is cystic does not rule out thyroid cancer. Thyroid fine needle aspiration (FNA) biopsy is the only non-surgical method that can differentiate malignant and benign nodules in most, but not all, cases