Parathyroid physiology Flashcards
- Describe the physiological roles for calcium and phosphate.
Calcium
- structural->bone
- 2nd messenger
- ca2+ dependent exocytosis
- Excitability–> decreased Ca2+= increased excitability
- —due to charge screening and perceived potential
Phosphate
- structural-> bone
- energy storage/currency
- essential component of RNA and DNA
- regulation of cellular systems through phosphorylation
- Illustrate the various compartments involved in calcium and phophate homeostasis and identify the mechanisms for distribution of calcium and phosphate between plasma and the bone.
Gut, Feces, Kidney, Urine, Bone
Blood- 8-10 mg/dL, 50 % is bound to albumins, 10 % as a salt, 40% free
osteocytic process-net exchange of 10 grams of calcium per day
osteoclastic property–> slow, net exchange of 280 mg/day of both calcium and phosphate
- Describe the regulation of PTH release.
peptide hormone, calcium dependent exocytosis from chief cells in para thyoid gland
- -when calcium gets low, parathyroid goes high
- there is a calcium sensor (Gq) on the cell surface. when receptor is not bound, PTH released
- List the actions of PTH.
excretes phosphate in the urine
holds onto calcium in the kidney
increases the hydroxylation of vit D3 to absorb calcium from gut
- Diagram the steps of Vitamin D synthesis and their regulation.
Vit D3 is produced in the skin or absorbed in the gut. In the liver it is hydroxylated to 25-OH-D3 in th eliver, its then hydroxylated again to 1,25-(OH)2-D3 (active form) in the kidney or deactivated into 24,25-(OH)2-D3 in the kidney
- List the actions of Vitamin D.
promotes gut absopriton of calcium by increasing calbindin on all cells in the intestinal wall
what is normal serum calcium
what is normal serum phosphate
8-10 mg/dL
3-6 mg/dL
how much calcium is bound to albumins?
50%
what is net change of osteocytic process per day?
what is net change of osteoclastic process per day?
10 grams of calcium only
280 mg of both calcium and phophate
what is psuedo hyperparathyoidism?
PTH receptors dont work