Thyroid test is to know whether the function of the thyroid gland is normal or not. The thyroid gland is located in the neck below the cartilage on both sides of the trachea and is a major endocrine gland of the human body. Thyroid hormones promote metabolism, increase the excitability of the central nervous system, and promote the growth and development of infants and children. There are three thyroid tests: 1. Thyroxine. It is also often referred to as T4, which is the main substance in the hormone secreted by the thyroid gland, and the value of T4 measurement is mainly used for the diagnosis of hyperthyroidism and hypothyroidism and for late monitoring.2, Triiodothyronine. It is also known as T3, and the T3 value mainly reflects whether the thyroid function is normal or not.3. Thyrotropin. The hormone secreted by the pituitary gland to promote the growth of the thyroid gland. When the thyrotropin is high, it is hypothyroidism, and when it is low, it is hyperthyroidism. Through these three tests, it can be determined whether there is any abnormality in the thyroid gland.