Calcium Metabolism Disorders Overview Quiz
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Questions and Answers

What is the primary function of calcium in the body?

  • Coenzyme for coagulation factors
  • Intracellular second messenger for hormone secretion
  • Structural support for bones and teeth (correct)
  • Control of excitability and nerve impulses

    • Which form of calcium in the plasma is considered physiologically active?

  • Bound to phosphates
  • Complexed with citrates
  • Protein-bound to albumin
  • Ionized (Ca2+) (correct)

    • What happens if there are derangements in calcium metabolism?

  • Hypernatremia
  • Hyperkalemia
  • Acidosis
  • Hypercalcemia or hypocalcemia (correct)

    • Which of the following is NOT a function of calcium in the body?

    <p>Second messenger for neurotransmitter release</p> Signup and view all the answers

    What percentage of calcium in the plasma is protein-bound to albumin?

    <p>40%</p> Signup and view all the answers

    Which mineral is the most abundant in the body after calcium?

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

    What is the primary function of parathyroid hormone (PTH) in the body?

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

    Which of the following is NOT a signaling pathway activated by the binding of PTH to its receptor?

    <p>Increased protein kinase A</p> Signup and view all the answers

    What is the primary effect of PTH on the kidney?

    <p>Decreases glomerular filtration rate</p> Signup and view all the answers

    What is the primary mechanism by which an increase in plasma calcium concentration suppresses PTH secretion?

    <p>Increased activation of the calcium-sensing receptor on parathyroid cells</p> Signup and view all the answers

    What is the difference between the rapid and delayed actions of PTH on bone?

    <p>Rapid action increases bone resorption, delayed action increases bone formation</p> Signup and view all the answers

    What is the primary mechanism by which PTH increases plasma calcium levels?

    <p>Stimulating calcium release from the bones</p> Signup and view all the answers

    What is the primary stimulus that leads to the release of parathyroid hormone (PTH) in secondary hyperparathyroidism?

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

    What is the mechanism by which decreased intestinal absorption of vitamin D leads to secondary hyperparathyroidism?

    <p>Decreased mobilization of calcium from bones due to end-organ resistance to PTH</p> Signup and view all the answers

    What is the major role of PTH in bone metabolism?

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

    In end-stage renal failure, what is the primary mechanism leading to the development of secondary hyperparathyroidism?

    <p>Decreased synthesis of 1,25-DHCC in the remaining functioning renal tubules</p> Signup and view all the answers

    How does PTH affect plasma calcium levels?

    <p>Increases plasma calcium levels</p> Signup and view all the answers

    Which of the following biochemical findings would be expected in a patient with primary hyperparathyroidism?

    <p>Elevated serum calcium, normal serum phosphate, and elevated PTH</p> Signup and view all the answers

    Which enzyme catalyzes the hydroxylation of cholecalciferol in the liver?

    <p>25-hydroxylase</p> Signup and view all the answers

    What is the primary mechanism by which increased intracellular phosphate levels in end-stage renal failure lead to secondary hyperparathyroidism?

    <p>Increased intracellular phosphate directly inhibits the activity of the 1-hydroxylase enzyme in the remaining functioning renal tubules</p> Signup and view all the answers

    Where is the 1-alpha hydroxylase enzyme located for the conversion of calcidiol to calcitriol?

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

    What is the result of PTH stimulating bone stem cells?

    <p>Increase in osteoclasts</p> Signup and view all the answers

    What is the net result of vitamin D activation by PTH?

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

    How does calcitriol promote the absorption of calcium and phosphate from the gut lumen to the plasma compartment?

    <p>By acting on osteoblastic activity</p> Signup and view all the answers

    Which hormone is responsible for inhibiting osteoclast activity through increased cAMP concentrations?

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

    Why does calcitonin decrease plasma calcium levels?

    <p>By increasing urine excretion of calcium and phosphate</p> Signup and view all the answers

    When is plasma calcitonin elevated?

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

    How does calcitonin protect against calcium loss during pregnancy and lactation?

    <p>By promoting calcium mobilization from the skeleton</p> Signup and view all the answers

    What is the main target cell for calcitonin's activity?

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

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