TY - CHAP M1 - Book, Section TI - Thyroid Disorders A1 - Blake, Elizabeth W. A2 - Sutton, S. Scott Y1 - 2019 N1 - T2 - McGraw-Hill's NAPLEX® Review Guide, 3e AB - The thyroid gland is located in the front of the neck and operates via negative feedback to synthesize thyroid hormones. The hypothalamus produces thyrotropin-releasing hormone (TRH) which stimulates the pituitary to release thyroid-stimulating hormone (TSH). TSH, also known as thyrotropin, stimulates the synthesis and release of thyroid hormones from the thyroid gland. Formation of thyroid hormones requires iodination of tyrosine residues by thyroid peroxidase to produce monoiodinated and diiodinated residues that couple to form triiodothyronine (T3) and levothyroxine (T4). Circulating levels of T3 and T4 regulate TSH secretion via negative feedback. The thyroid gland is responsible for the production of T4 and less than 20% of T3. Peripheral conversion of T4 to T3 forms the majority of T3. Compared to T4, T3 is more potent, less bound to plasma proteins, and has a shorter half-life. Thyroid hormones affect multiple organ systems throughout the body and alterations in hormone concentrations and TSH lead to hyper- or hypothyroidism (Tables 62-1 and 62-2). SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/04/18 UR - accesspharmacy.mhmedical.com/content.aspx?aid=1158316462 ER -