There are many causes of goiter, the most common of which include the following four: First, hyperthyroidism, commonly known as hyperthyroidism. Secondly, simple goiter. Third, thyroid cancer. Fourth, chronic lymphatic thyroiditis, also known as Hashimoto’s thyroiditis. To further clarify what causes the goiter, the following tests can be performed, including the function of the thyroid gland, which is indicated when the thyroid gland is hyperactive. In the case of simple goiter, the results of the thyroid function test are normal. Other tests include ultrasonography of the thyroid gland, which is the most commonly used test, and thyroid-specific antibody tests.