Parathyroid Hormone (PTH) Structure and Function
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Questions and Answers

How many amino acids are present in the preproPTH molecule?

  • 115 (correct)
  • 90
  • 84
  • 99
  • Which region of the PTH molecule is primarily responsible for receptor binding?

  • 1-25
  • 50-84
  • 1-34
  • 25-34 (correct)
  • Which action is NOT a function of PTH on calcium homeostasis?

  • Decreasing intestinal calcium absorption (correct)
  • Increasing calcium absorption from intestines
  • Promoting bone resorption to release calcium
  • Reducing renal calcium clearance
  • In prolonged dietary calcium deficiency, how does PTH prevent hypocalcemia?

    <p>At the expense of bone substance</p> Signup and view all the answers

    Which mineral is typically released from bone along with calcium due to PTH activity?

    <p>Phosphate</p> Signup and view all the answers

    What is the role of 1.25 (OH)2 D3 in the calcium homeostasis maintained by PTH?

    <p>Increasing intestinal calcium absorption</p> Signup and view all the answers

    How does PTH affect renal phosphate clearance?

    <p>Increases it</p> Signup and view all the answers

    Which phase(s) of bone does PTH act upon to increase the ECF calcium concentration?

    <p>Both organic and inorganic phases</p> Signup and view all the answers

    Study Notes

    Chemistry of PTH

    • PTH consists of 84 amino acids
    • Formed by parathyroid glands from a precursor molecule called preproPTH (115 amino acids)
    • PreproPTH forms proPTH (90 amino acids), which then forms PTH
    • PTH is stored in the parathyroid gland to be released on need
    • PTH 1-34 amino acids has full biologic activity
    • Region 25-34 of PTH is primarily responsible for receptor binding

    Function of PTH

    • Net effect of PTH on bone and kidney is to increase ECF calcium concentration
    • Net effect of PTH on bone and kidney is to decrease ECF phosphate concentration

    Effects of PTH on Calcium Homeostasis

    • In acute hypocalcemia, PTH restores normal ECF calcium concentration
    • PTH acts indirectly on the intestinal mucosa through stimulation of 1.25 (OH)2 D3
    • PTH acts directly on the kidneys and bone
    • PTH reduces the clearance or excretion of calcium, increasing ECF concentration
    • PTH increases the rate of dissolution of bone, moving Ca+2 ions into ECF
    • PTH increases the efficiency of absorption from the intestine by promoting the synthesis of 1.25 (OH)2 D3
    • In prolonged dietary Ca deficiency, PTH prevents hypocalcemia at the expense of bone substance

    PTH Affects Phosphate Homeostasis

    • Phosphate is released with calcium from bone whenever PTH dissolves the mineral matrix
    • PTH increases renal phosphate clearance

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    Description

    This quiz covers the chemistry and function of Parathyroid Hormone (PTH), including its formation, storage, and biological activity in the body.

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