1. Parathyroid Hormone
By Ezinne Akudinobi

3. 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

4. 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.

5. Parathyroid Hormone Polypeptide hormone Consists of 84 amino acids
Regulator of Calcium Homeostasis
Target Organs: bone, kidneys, and small intestine
Normal Blood Value: pg/mL
Hypersecretion → tetany
Hyposecretion → osteomalacia

6. Structure : PTH (1-34)

7. Structure

8. 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

9. 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

10. Review: G-protein-coupled receptor

11. 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

12. Negative Feedback Loop

13. Serum Calcium

14. Vitamin D Synthesis

15. REFERENCES https://medlineplus.gov/ency/article/003690.htm