Parathyroid physiology Flashcards

1
Q
  1. Describe the physiological roles for calcium and phosphate.
A

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
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2
Q
  1. 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.
A

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

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3
Q
  1. Describe the regulation of PTH release.
A

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
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4
Q
  1. List the actions of PTH.
A

excretes phosphate in the urine

holds onto calcium in the kidney

increases the hydroxylation of vit D3 to absorb calcium from gut

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5
Q
  1. Diagram the steps of Vitamin D synthesis and their regulation.
A

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

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6
Q
  1. List the actions of Vitamin D.
A

promotes gut absopriton of calcium by increasing calbindin on all cells in the intestinal wall

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7
Q

what is normal serum calcium

what is normal serum phosphate

A

8-10 mg/dL

3-6 mg/dL

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8
Q

how much calcium is bound to albumins?

A

50%

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9
Q

what is net change of osteocytic process per day?

what is net change of osteoclastic process per day?

A

10 grams of calcium only

280 mg of both calcium and phophate

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10
Q

what is psuedo hyperparathyoidism?

A

PTH receptors dont work

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