Hormonas Tiroideas y Cerebro. Notas Sobre La Relación Bocio y ...

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Bibliografía 1. Eknoyan G. 2004. Emergence of the concept of endocrine function and endocrinology. Adv Chronic Kidney Dis 11: 371-376 2. Henderson J. 2005. Ernest Starling and “hormones”: an historical commentary. J Endocrinol. 184: 5-10 3. Hillier SG. 2005. 100 years of hormones: pathway biology as the fifth force in endocrinology. J Endocrinol. 184: 3-4 4. Tata JR. 2005. One hundred years of hormones. EMBO. 6: 490-496 5. Medvei VC. A History of Endocrinology. MTP Press Limited. Falcon House. <strong>La</strong>ncaster, England, 1982 6. Merke, F. History and Iconography of Endemic Goitre and Cretinism. <strong>La</strong>ncaster, MTP Press. England, 1984 7. Miles M. 1998. Goitre, cretinism and iodine in South Asia: historical perspectives on a continuing scourge. Med Hist 42: 47-67 8. Leoutsakos V. 2007. A Short history of the thyroid gland. Hormones 3: 268-271 9. Asimov, I. Asimov’s Biographical Encyclopedia of Science and Technology. Doubleday & Co., Inc. Garden City, N. Y. 1972 10. Giampalmo A. 1996. The endemic goiter in figurative arts. Med Secolli 8: 85-103 11. Vescia FG and Basso L. 1997. Goiter in the Renaissance. Vesalius 3: 23-32 12. Droin G. 2005. Endemic goitre and cretinism in Alps: evolution of science and treatments, transformation of the pathology and its representations. Internat J Anthropol 20: 307-324 13. Sawin TC. Defining thyroid hormone: its nature and control. En: Endocrinology. People and Ideas. SM McCann (edit). American Physiological Society. Waverly Press, Inc. Baltimore, Maryland, 1988 14. Valverde-R C. Intercomunicación Celular y Neuroendocrinología: Estrategias y Mecanismos de Control y Regulación Celular. En: Aproximaciones de las Neurociencias a la Conducta. M Corsi Cabrera (Comp) pp. 261- 284. Facultad de Psicología UNAM, México, 1996. 15. Bondeson L and Bondeson A-G. 2003. Michelangelo’s divine goitre. J R Soc Med 96: 609-611 16. Saunders JB de CM and O’Malley CD. The Anatomical Drawings of Andreas Vesalius. Bonanza Books, New York, 1982 17. Siddiqui M A, Mehta N J and Khan I A. 2003. Paracelsus: the Hippocrates of the Renaissance. J Med Biography 11: 78-80 18. Cherici C. 2006. Vincenzo Malacarne (1744-1816): a researcher in neurophysiology between anatomophysiology and electrical physiology of the human brain. C R Biologies 329: 319-329 6
Thyroid hormone synthesis Peter Kopp, Liuska Pesce, Sabine Schnyder, Juan Carlos Solis-S Division of Endocrinology, Metabolism and Molecular Medicine, Feinberg School of Medicine, Northwestern University, Chicago IL 60611, USA Overview on Thyroid Hormone Synthesis Thyroid hormone biosynthesis, storage, and secretion require a series of highly regulated steps (1, 2). Iodide, the rate-limiting substrate for thyroid hormone synthesis, is actively transported into thyroid follicular cells by the sodium-iodide symporter (NIS) at the basolateral membrane (Figure 1) (3). At the apical membrane, iodide efflux into the follicular lumen is mediated, at least in part, by pendrin (PDS/SLC26A4) (4). On the luminal side of the apical membrane, iodide is oxidized by thyroperoxidase (TPO), a reaction that requires the presence of hydrogen peroxide (H 2 O 2 ) (1, 2). H 2 O 2 is generated by a calcium-dependent flavoprotein enzyme system that includes the NADPH oxidase THOX2 (5, 6). In the follicular lumen, thyroglobulin (TG) serves as matrix for the synthesis of T4 and T3 (7). In a first step, TPO iodinates selected tyrosyl residues on TG, a process referred to as organification or iodination. This results in the formation of mono- and diiodotyrosines (MIT, DIT). In the subsequent coupling reaction, which is also catalyzed by TPO, two iodotyrosines are coupled to form T4 or T3. Iodinated TG is stored as colloid in the follicular lumen. In response to demand for thyroid hormone secretion, TG is internalized into the follicular cell by micro- and macropinocytosis, and digested in lysosomes. Subsequently, the thyronines T4 (~80%) and T3 (~20%) are released into the blood stream. MIT and DIT are deiodinated by the intracellular iodotyrosine dehalogenase 1 (DEHAL1) (8), and the released iodide is recycled for hormone synthesis. Thyroid hormone synthesis is dependent on the nutritional availability of iodine and predominantly regulated by TSH. TSH binds to its cognate receptor, a member of the G protein coupled seven trans-membrane receptors, which is expressed at the basolateral membrane (Figure 1). Binding of TSH to its receptor leads primarily to coupling to Gsαand subsequent activation of adenylyl cyclase. The increase in cAMP leads to phosphorylation of protein kinase A and to activation of targets in the cytosol and the nucleus. The TSH-dependent cAMP cascade is the major regulator of growth, differentiation, and hormone secretion of thyroid follicular cells. At higher doses of TSH, stimulation of Gq and the phospholipase C- dependent inositol phosphate Ca 2+ - diacylglycerol pathway acti-vates H 2 O 2 generation and iodination. Figure 1 H 2 O 2 Generation Iodination IP3 PKC DAG PLC Gq CREB CREM PAX8 TTF1 TTF2 PIP2 TSH Differentiation Growth Hormone Synthesis ATP Gs PKA cAMP AC I - or HOI PDS I - I - Organification TG TPO H2O2 Dehalogenase NIS MIT DIT Thox2 NADPH + NADPH MIT DIT Na/K-ATPase Na K Coupling TPO O2 TG MIT DIT T4 T3 Hydrolysis T3 T4 T3 T4 7
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