Parathyroid Hormone By Ezinne Akudinobi

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Function from Endocrinology: An Integrated Approach,2001 Calcium Phosphate Bone growth and remodeling Secretion (exocytosis) Excitation-contraction coupling Stabilization of membrane potentials Enzyme co-factor (e.g. in blood coagulation) Second messenger Formation of: High energy compounds e.g. ATP, creatinine phosphate Second messengers e.g. cAMP, inositol phosphates Component of: DNA/RNA Phospholipid membranes Bone Phosphorylation (activation/inactivation) of enzymes Intracellular anion Box 5.1: Nussey S., Whitehead Endocrinology: An Integrated Approach. Oxford. BIOS Scientific Publishers; 2001

Parathyroid Gland Located in anterior neck. Embedded in the posterior surface of the thyroid gland. Pair of oval glands on each lobe, but anomalies may occur. Contains chief cells and oxyphil cells. Secretes parathyroid hormone, PTH.

Parathyroid Hormone Polypeptide hormone Consists of 84 amino acids Regulator of Calcium Homeostasis Target Organs: bone, kidneys, and small intestine Normal Blood Value: 10-55 pg/mL Hypersecretion → tetany Hyposecretion → osteomalacia http://dossier.univ-st-etienne.fr/lbti/www/Mednucl/AtlasEnd/parathy/image/base5.gif

Structure : PTH (1-34) https://pubchem.ncbi.nlm.nih.gov

Structure

Synthesis Expression is initiated by the calcium sensors located in the chief cells of parathyroid gland. Synthesized from precursor molecule 115 amino acids Rough Endoplasmic Reticulum 90 amino acids Golgi apparatus 6 amino acids cleaved https://www.ncbi.nlm.nih.gov/books/NBK24/

Receptor: Structure G protein-couple receptor Type 1: Type 2 Bone and kidney Type 2 Brain and testes 7 membrane-spanning helixes. ~150 amino acid amino terminal extracellular domain http://ajprenal.physiology.org/content/277/5/F665

Review: G-protein-coupled receptor http://cnx.org/contents/GFy_h8cu@9.87:H4oMpCSi@7/Signaling-Molecules-and-Cellul

Receptor: Function AC: Adenylyl cyclase PLC: phospholipase C AC signaling pathway increases PTH secretion PLC signaling pathway increases intracellular calcium concentration Pathway dependent on the presence of the Na+/H+ regulatory factor, NHERF1 http://ajprenal.physiology.org/content/ajprenal/290/5/F975/F3.large.jpg?width=800&height=600&carousel=1

Negative Feedback Loop

Serum Calcium http://www.nbs.csudh.edu/chemistry/faculty/nsturm/CHE452/images/CaSensor.gif

Vitamin D Synthesis

REFERENCES https://medlineplus.gov/ency/article/003690.htm http://jasn.asnjournals.org/content/22/2/216.full.pdf+html http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/thyroid/pth.html https://www.ncbi.nlm.nih.gov/books/NBK24/ http://www.nature.com/nrc/journal/v7/n9/fig_tab/nrc2196_F1.html http://ajprenal.physiology.org/content/277/5/F665#sec-3 http://teachmeanatomy.info/neck/viscera/parathyroid-glands/