Thyroiditis

The thyroid gland is the largest endocrine gland of the human body. It is located under the thyroid cartilage directly next to the third trachea and in front of the four cartilage rings. It consists of both lateral leaves and isthmus. The average weight is about 20-25g. There are 4 parathyroid glands and recurrent laryngeal nerve behind the thyroid. The blood supply has four arteries: up, down, left, right, and so on. The thyroid is rich in blood supply. The glands are dominated by the sympathetic and vagus nerves of the cervical sympathetic ganglia. The main function of the thyroid is to synthesize thyroid hormones and regulate metabolism. -200μg inorganic iodine compound, which is absorbed into the blood circulation through the gastrointestinal tract, quickly concentrates the thyroid gland, and the iodine stored in the gland is about 1/5 of the whole body. After the iodide enters the cell, through the action of oxidase, the active iodine is rapidly combined with the tyrosine group on the thyroglobulin molecule in the glial cavity to form monoiodotyrosine (MIT) and diiodotyrosine ( DIT), iodized tyrosine couples MIT and DIT to form thyroxine (T4) through the action of oxidase, and MID and DIT couple to form triiodothyronine (T3), which is stored in the glia cavity. Synthetic thyroxine (T4) and triiodothyronine (T3) are secreted into the blood circulation and mainly bind to thyroxine-binding globulin (TBG) in the plasma to facilitate transport and regulate the concentration of thyroxine in the blood. Thyroxine (T4) is deiodinated in peripheral tissues to form stronger biologically active T3 and inactive rT3, respectively. The removed iodine can be reused. Therefore, blood T4, T3, and rT3 increased during hyperthyroidism, and all of them were lower than normal when hypothyroidism decreased. Thyroxine secretion is secreted by pituitary cells and TSH is regulated by the adenylyl cyclase-cAMP system. TSH is controlled by the TRH secreted by the hypothalamus, which forms the hypothalamic-pituitary-thyroid axis and regulates thyroid function.

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