Parathyroid Hormone Structure and Function
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Questions and Answers

Which time of day is plasma PTH levels the highest?

  • In the early hours of the morning (correct)
  • At noon
  • In the evening
  • In the afternoon

    • What is the net effect of the activation by intact PTH at the renal tubule?

  • Increases the reabsorption of phosphate and bicarbonate
  • Lowers plasma [Ca2+]
  • Increases GFR (correct)
  • Decreases the reabsorption of calcium and magnesium

    • Where are the high levels of the parathyroid hormone 1 receptor located?

  • Central nervous system
  • Liver
  • Bone (correct)
  • Pancreas

    • Which signaling pathway is activated upon binding of PTH to its receptor?

    <p>Increased phospholipase C</p> Signup and view all the answers

    What action does PTH have on the distal tubule in the kidney?

    <p>Activates specific receptors</p> Signup and view all the answers

    What is the rapid action associated with PTH in bone?

    <p>Begins within minutes</p> Signup and view all the answers

    What inhibits the activity of 1α-hydroxylase?

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

    Which enzyme catalyzes the hydroxylation of 25-HCC to 24:25-DHCC?

    <p>24-hydroxylase</p> Signup and view all the answers

    What promotes the intestinal reabsorption of calcium?

    <p>Calbindin-D</p> Signup and view all the answers

    Which protein is released into the bloodstream during bone formation?

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

    What can be used as a marker of bone formation and turnover?

    <p>Serum alkaline phosphatase levels</p> Signup and view all the answers

    What stimulates the mature osteoclasts leading to bone resorption?

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

    What is the most common single presenting complaint in Primary Hyperparathyroidism?

    <p>Renal stones</p> Signup and view all the answers

    What is the most serious complication of Primary Hyperparathyroidism?

    <p>Deposition of calcium in kidney tubules resulting in impaired renal function</p> Signup and view all the answers

    Which of the following is NOT a characteristic feature of Secondary Hyperparathyroidism?

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

    What causes hypercalcemia in Primary Hyperparathyroidism?

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

    In Primary Hyperparathyroidism, what is responsible for the autonomous production of PTH?

    <p>Parathyroid adenoma</p> Signup and view all the answers

    Which organ is most commonly affected in Primary Hyperparathyroidism?

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

    What is the primary target cell for calcitonin?

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

    What is the effect of calcitonin on osteoblastic activity?

    <p>It increases osteoblastic activity</p> Signup and view all the answers

    During which periods is plasma [calcitonin] elevated?

    <p>During pregnancy and lactation</p> Signup and view all the answers

    What is the mechanism by which calcitonin reduces plasma [Ca2+]?

    <p>By decreasing renal reabsorption of calcium and phosphate</p> Signup and view all the answers

    What is the effect of calcitonin on PTH activity?

    <p>It counteracts PTH activity</p> Signup and view all the answers

    How does calcitonin protect against calcium loss from the skeleton?

    <p>By protecting against calcium loss during periods of calcium mobilization</p> Signup and view all the answers

    What is the effect of PTH on osteoclasts?

    <p>It stimulates their formation and activity</p> Signup and view all the answers

    What is the role of 25-hydroxylase in vitamin D metabolism?

    <p>It catalyzes the formation of 25-hydroxycholecalciferol</p> Signup and view all the answers

    What is the location of the 1α-hydroxylase enzyme?

    <p>In the proximal convoluted tubules of the nephrons</p> Signup and view all the answers

    What is the result of PTH stimulating osteoblast activity?

    <p>An increase in plasma calcium levels</p> Signup and view all the answers

    What is the role of vitamin D-binding protein?

    <p>It transports cholecalciferol to the liver</p> Signup and view all the answers

    What is the effect of PTH on plasma Ca2+ and phosphate levels?

    <p>It increases plasma Ca2+ and phosphate levels</p> Signup and view all the answers

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