Hypothyroidism is a common clinical condition of the thyroid gland, mainly due to chronic lymphocytic thyroiditis, thyroid iodine-131 therapy or post-operative thyroid surgery. Laboratory tests may reveal a significant increase in thyroid stimulating hormone levels in the thyroid triad. Free thyroid hormone and free triiodothyronine hormone levels are low. Regardless of the cause of hypothyroidism, euthyroid replacement therapy is given clinically. This medication is usually taken orally in the morning half an hour before meals on an empty stomach, and the thyroid function is rechecked once in about 4 weeks.