Anatomy and Physiology of the Thyroid Gland
The thyroid gland and its main product, thyroid hormone, play a very important role in human physiology. As such, detailed knowledge of thyroid gland embryology, anatomy, and physiology is critical for any physician managing patients with thyroid disorders. The thyroid gland is shield-shaped organ located anteriorly to the trachea in the lower neck. A variety of conditions ranging from variations or errors in the development and migration of the gland during organogenesis to mutations that lead to thyroid dysfunction can have profound effects on the human homeostasis. New insides, such as thyroid cell clonality provide potentially important clues to thyroid carcinogenesis. Any surgeon performing thyroid surgery needs to have intimate knowledge of the anatomy of the thyroid gland and its surrounding structures as well as the large numbers of variations they might encounter. Thyroid hormone plays an important role in the function of practically all human organs and tissues. Its function is under an elaborate regulation the complexity of which we understand only partially. The hypothalamic-pituitary-thyroid axis provides the classical endocrine negative feedback regulation, although there is clear evidence today that each tissue may have its own unique regulatory system as well.
The molecular biology of thyroid function is being studied in great detail. Clinically important molecules, like the thyroid-stimulating hormone receptor and the sodium iodide symporter, have been identified and well characterized. Such discoveries have significantly improved our understanding of thyroid physiology. As a result, new diagnostic and therapeutic approaches for the management of thyroid disorders are now available or in development.
KeywordsThyroid anatomy and physiology Thyroid hormone Hypothalamic-pituitary-thyroid axis Thyroid receptors Deiodinase
- 1.Braverman LE, Cooper D. Werner and Ingbar’s the thyroid. Philadelphia, PA: Lippincott Williams and Wilkins; 2012.Google Scholar
- 4.De Groot LJ, Beck-Peccoz P, Chrousos G, et al. Impaired sensitivity to thyroid hormone: defects of transport, metabolism and action. 2000.Google Scholar
- 9.Jovanovic L, Delahunt B, McIver B, Eberhardt NL, Grebe SKG. Thyroid gland clonality revisited: the embryonal patch size of the normal human thyroid gland is very large, suggesting X-chromosome inactivation tumor clonality studies of thyroid tumors have to be interpreted with caution. J Clin Endocrinol Metab. 2003;88(7):3284–91. https://doi.org/10.1210/jc.2002-021552.CrossRefPubMedGoogle Scholar
- 12.Lan XB, Zhang H. An introduction of surgical update in 2015 American thyroid association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer. Zhonghua Wai Ke Za Zhi. 2016;54(3):172–6. https://doi.org/10.3760/cma.j.issn.0529-5815.2016.03.004.CrossRefPubMedGoogle Scholar
- 26.Mumusoglu S, Beksac MS, Ekiz A, Ozdemir P, Hascelik G. Does the presence of autoantibodies without autoimmune diseases and hereditary thrombophilia have an effect on recurrent pregnancy loss? J Matern Fetal Neonatal Med. 2016;29(14):2352–7. https://doi.org/10.3109/14767058.2015.1085964.CrossRefPubMedGoogle Scholar
- 45.Gullberg H, Rudling M, Forrest D, Angelin B, Vennström B. Thyroid hormone receptor beta-deficient mice show complete loss of the normal cholesterol 7alpha-hydroxylase (CYP7A) response to thyroid hormone but display enhanced resistance to dietary cholesterol. Mol Endocrinol. 2000;14(11):1739–49. https://doi.org/10.1210/mend.14.11.0548.CrossRefPubMedGoogle Scholar
- 52.Lin H-Y, Sun M, Tang H-Y, et al. L-Thyroxine vs. 3,5,3′-triiodo-L-thyronine and cell proliferation: activation of mitogen-activated protein kinase and phosphatidylinositol 3-kinase. Am J Physiol Cell Physiol. 2009;296(5):C980–91. https://doi.org/10.1152/ajpcell.00305.2008.CrossRefPubMedGoogle Scholar