Vitamin D Metabolism and Synthesis
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Questions and Answers

What is the location where the conversion of 25-OH-D3 to 1,25-(OH)2D3 takes place?

  • Proximal convoluted tubule (correct)
  • Distal convoluted tubule
  • Small intestine
  • Liver

    • Who demonstrated the conversion of 25-OH-D3 to 1,25-(OH)2D3?

  • Fraser and Kodicek (correct)
  • DeLuca
  • HF DeLuca and Kodicek
  • Holick et al.

    • What is the name of the enzyme responsible for the conversion of vitamin D3 to 25-OH-D3?

  • CYP2R1 (correct)
  • CYP27B1
  • CYP11A1
  • CYP24A1

    • What is the function of the vitamin D system suggested by the presence of CYP27B1 in several cells?

    <p>Paracrine/autocrine function</p> Signup and view all the answers

    What is the reason for the elimination of the liver as the site of conversion of 25-OH-D3 to 1,25-(OH)2D3?

    <p>Subtotal hepatectomy</p> Signup and view all the answers

    What is the consequence of the discovery of vitamin D?

    <p>Establishment of the vitamin D endocrine system</p> Signup and view all the answers

    What is the significance of the cloning of CYP27B1?

    <p>Understanding of the autocrine function of the vitamin D system</p> Signup and view all the answers

    What is the primary function of fibroblast growth factor 23 (FGF23) in calcium regulation?

    <p>To decrease serum phosphorus levels</p> Signup and view all the answers

    What is the primary site of 1,25(OH)2D3 production?

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

    What is the effect of calcitonin on calcium levels?

    <p>Decreases calcium reabsorption in the kidney</p> Signup and view all the answers

    What is the role of parathyroid hormone (PTH) in calcium regulation?

    <p>To increase serum calcium levels</p> Signup and view all the answers

    What is the enzyme responsible for converting 25-OH-D3 to 1,25(OH)2D3?

    <p>CYP2R1</p> Signup and view all the answers

    Where does the conversion of 25-OH-D3 to 1,25-(OH)2D3 take place?

    <p>In the kidney</p> Signup and view all the answers

    What is the effect of a high-calcium diet on vitamin D metabolism?

    <p>Decreases vitamin D production</p> Signup and view all the answers

    What is the result of feeding a low-calcium diet to an animal?

    <p>An increase in 1,25-(OH)2D3 levels</p> Signup and view all the answers

    What is the role of parathyroid hormone (PTH) in vitamin D regulation?

    <p>To stimulate the synthesis of 1,25-(OH)2D3</p> Signup and view all the answers

    What is the role of estrogens in bone mineral homeostasis?

    <p>Suppresses bone resorption</p> Signup and view all the answers

    What is the outcome when the parathyroid glands are removed from an animal?

    <p>A decrease in 1,25-(OH)2D3 levels</p> Signup and view all the answers

    What is the effect of a high-calcium diet on 1,25-(OH)2D3 synthesis?

    <p>It suppresses the synthesis of 1,25-(OH)2D3</p> Signup and view all the answers

    What is the role of the 1a-hydroxylase enzyme in vitamin D metabolism?

    <p>To convert 25-OH-D3 to 1,25-(OH)2D3</p> Signup and view all the answers

    What is the mechanism by which the parathyroid glands sense hypocalcemia?

    <p>Through the detection of low calcium levels by the parathyroid glands</p> Signup and view all the answers

    What percentage of bisphosphonates is absorbed when taken orally?

    <p>Less than 10%</p> Signup and view all the answers

    What is the primary mechanism of action of cinacalcet?

    <p>Blocks PTH secretion</p> Signup and view all the answers

    What is a primary difference between etidronate and other bisphosphonates?

    <p>It causes less gastric irritation</p> Signup and view all the answers

    What is the primary therapeutic use of plicamycin (mithramycin)?

    <p>Paget's disease treatment</p> Signup and view all the answers

    What is the effect of raloxifene on breast tissue?

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

    What is the effect of intermittent low-dose PTH on bone?

    <p>Increases bone formation without stimulating bone resorption</p> Signup and view all the answers

    What is the primary mechanism of action of raloxifene on bones?

    <p>Selectively activates estrogen receptors</p> Signup and view all the answers

    What is the mechanism of action of Teriparatide in osteoporosis treatment?

    <p>Stimulating new bone formation</p> Signup and view all the answers

    What is the frequency of Prolia (Denosumab) administration for postmenopausal osteoporosis?

    <p>Two shots a year</p> Signup and view all the answers

    What is the molecular weight of Denosumab?

    <p>147 kDa</p> Signup and view all the answers

    What is the primary function of calcitonin in serum calcium homeostasis?

    <p>Secondary regulation of serum calcium homeostasis</p> Signup and view all the answers

    What is the class of compounds that bisphosphonates are analogues of?

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

    What is the consequence of osteonecrosis of the jaw bone in osteoporosis treatment?

    <p>Jaw bone problem</p> Signup and view all the answers

    What is the role of bones in calcium homeostasis?

    <p>Calcium reservoir</p> Signup and view all the answers

    What is the primary function of PTH in osteoporosis treatment?

    <p>Stimulating bone formation</p> Signup and view all the answers

    What is the common side effect of Denosumab treatment?

    <p>All of the above</p> Signup and view all the answers

    What is the frequency of Teriparatide injection in osteoporosis treatment?

    <p>Daily injection</p> Signup and view all the answers

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