Hypothyroidism is a common endocrine disorder resulting from a deficiency of thyroid hormones (TH). Worldwide, iodine deficiency is the most common cause of hypothyroidism; however, in Poland and other areas of adequate iodine intake, chronic autoimmune thyroiditis—the Hashimoto’s disease also known as the Hashimoto thyroiditis is the primary reason for hypothyroidism4,5. This evidence concerns the gene TH and hypothyroidism.