Bone Remodeling Quiz
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Questions and Answers

What is the role of osteoprotegerin (OPG) in bone remodelling?

  • Stimulates osteoclast progenitor differentiation
  • Acts as a decoy receptor for RANKL (correct)
  • Promotes osteoblast activity
  • Increases bone resorption in response to low calcium levels

    • Which hormone is primarily responsible for increasing calcium reabsorption in the kidneys?

  • Vitamin D
  • Parathyroid hormone (PTH) (correct)
  • Calcitonin
  • Estrogen

    • What effect does estrogen withdrawal during menopause typically have on bone density?

  • Promotes osteoporosis (correct)
  • Stabilizes the activity of osteoclasts
  • Stimulates bone formation
  • Increases mineralization of bone

    • How does calcitriol influence bone remodelling?

    <p>Stimulates calcium and phosphate absorption in the intestine</p> Signup and view all the answers

    Which of the following statements about bone resorption is true?

    <p>Bone resorption involves the interaction of RANKL and RANK.</p> Signup and view all the answers

    What affects the conversion of cholecalciferol to calcitriol?

    <p>Presence of phosphate concentration</p> Signup and view all the answers

    What is the primary daily calcium turnover in the human body?

    <p>700 mg</p> Signup and view all the answers

    Which of the following hormones is involved in both stimulating bone formation and resorption?

    <p>Parathyroid hormone (PTH)</p> Signup and view all the answers

    What is the primary role of osteoblasts in bone remodelling?

    <p>Form bone matrix components</p> Signup and view all the answers

    Which component is essential in linking calcium to collagen in the bone matrix?

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

    Which hormone is NOT involved in the process of bone remodelling?

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

    What initiates the process of bone remodelling in response to mechanical stress?

    <p>Secretion of sclerostin by osteocytes</p> Signup and view all the answers

    Osteoclasts are primarily derived from which lineage?

    <p>Macrophage-monocyte lineage</p> Signup and view all the answers

    Which of the following is a secondary function of bone, beyond providing structure?

    <p>Playing a role in calcium homeostasis</p> Signup and view all the answers

    What is the main structure that forms when osteoid is mineralized?

    <p>Bone matrix</p> Signup and view all the answers

    Which cell type is responsible for the activation of osteoclasts during bone remodelling?

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

    What is the mechanism of action of Denosumab?

    <p>Inhibits RANKL, mimicking OPG and inhibiting osteoclast differentiation</p> Signup and view all the answers

    What is the primary role of calcitriol in bone metabolism?

    <p>Increases the synthesis of osteocalcin</p> Signup and view all the answers

    Which of the following statements about osteoporosis is true?

    <p>Its common causes include postmenopausal deficiency of oestrogen.</p> Signup and view all the answers

    Which of the following is NOT an indication for the use of vitamin D analogues?

    <p>Treatment of osteoporosis in post-menopausal women</p> Signup and view all the answers

    Which of the following drugs is classified as an anabolic agent that increases bone formation?

    <p>PTH, teriparatide</p> Signup and view all the answers

    What is a major adverse effect of excessive vitamin D intake?

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

    What effect do bisphosphonates have on bone cells?

    <p>Inhibit the activity of osteoclasts</p> Signup and view all the answers

    How often is Denosumab administered subcutaneously?

    <p>Every 6 months</p> Signup and view all the answers

    Which of the following is a primary action of Romosozumab?

    <p>Inhibits osteoclast activity</p> Signup and view all the answers

    What is a common side effect associated with the use of bisphosphonates?

    <p>Atypical femoral fractures</p> Signup and view all the answers

    Which mineral is essential for the formation of ATP and is influenced by bone metabolism?

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

    What should be monitored during therapy with vitamin D?

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

    Which calcium salt has the highest absorption rate?

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

    What is a recommended dietary component to support bone health?

    <p>Adequate protein and calcium intake</p> Signup and view all the answers

    Which statement about the adverse reactions of oral calcium salts is accurate?

    <p>They can cause gastrointestinal disturbances</p> Signup and view all the answers

    How often should the use of bisphosphonates be reevaluated?

    <p>Every 5 years</p> Signup and view all the answers

    What is a potential side effect of calcium carbonate administration in patients with renal failure?

    <p>Arterial calcification</p> Signup and view all the answers

    Which mechanism of action is associated with cinacalcet in the treatment of hyperparathyroidism?

    <p>Enhancing parathyroid Ca2+-sensing receptor sensitivity</p> Signup and view all the answers

    What is a common adverse drug reaction (ADR) associated with teriparatide?

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

    What is the main therapeutic use of calcium salts?

    <p>Prevention and treatment of osteoporosis</p> Signup and view all the answers

    For how long should teriparatide treatment be limited according to safety concerns?

    <p>24 months</p> Signup and view all the answers

    What is the primary purpose of administering supplemental calcium and vitamin D after a zoledronate infusion?

    <p>To enhance the effectiveness of bisphosphonates</p> Signup and view all the answers

    Which condition can calcitonin be used to treat effectively?

    <p>Severe back pain in acute osteoporotic vertebral fractures</p> Signup and view all the answers

    What adverse effect is most commonly attributed to calcitonin?

    <p>Nausea and vomiting</p> Signup and view all the answers

    Which of the following statements regarding Raloxifene is correct?

    <p>It is effective for secondary prevention in postmenopausal women who cannot tolerate bisphosphonates.</p> Signup and view all the answers

    What is one of the mechanisms of action of calcitonin?

    <p>Induces osteoclast apoptosis</p> Signup and view all the answers

    For which disorder is long-term use of bisphosphonates most likely to require periodic re-evaluation?

    <p>Teeth osteonecrosis</p> Signup and view all the answers

    Which complication is a known adverse reaction of Raloxifene?

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

    How does calcitonin generally affect plasma calcium levels?

    <p>Decreases plasma [Ca2+]</p> Signup and view all the answers

    Study Notes

    Lesson 27: Calcium Homeostasis

    • Focuses on calcium homeostasis within the body, specifically relating to bone health.

    Index

    • Bone remodelling process
    • Disorders of bone
    • Non-pharmacological treatment
    • Drugs used in bone disorders

    Bone Remodelling Process

    • Regulated by osteoblasts (OB) and osteoclasts (OC).
    • Affected by various cytokines.
    • Turnover of bone minerals, particularly calcium and phosphate.
    • Several hormones (parathyroid hormone (PTH), vitamin D family, oestrogens, growth hormone, steroids, calcitonin) and various cytokines are also involved.
    • Bone matrix is the osteoid, mainly collagen.
    • Other components (proteoglycans, osteocalcin) participate.
    • Osteonectin binds calcium and collagen.
    • Deposition of calcium phosphate crystals (hydroxyapatite) converts osteoid into hard bone matrix.

    Osteoblasts

    • Cells forming bone, derived from precursors in bone marrow and periosteum.
    • Form important components of bone matrix, particularly collagen (osteoid).
    • Participate in activating osteoclasts.
    • Osteocytes—derived from osteoblasts embedded in bone matrix; they influence mechanical stress response, initiate bone remodelling and secrete sclerostin

    Osteoclasts

    • Multinucleated cells that resorb bone.
    • Derived from macrophage-monocyte lineage.
    • Other important cells in bone include macrophages/monocytes, lymphocytes and vascular endothelium cells, which secrete cytokines and mediators in bone remodelling.

    Activity of Osteoblasts and Osteoclasts

    • Bone formation, and resorption stages are outlined, with depictions of the differentiation processes to osteoblasts/osteoclasts
    • The processes are described in detail, including the cells, chemical actions and outcomes.

    Bone Remodelling and Osteoclasts/Osteoblasts Activity

    • RANKL interacts with RANK to activate osteoclasts.
    • OPG (osteoprotegerin) acts as a decoy receptor for RANKL, inhibiting osteoclast differentiation and activation.

    Regulation of Bone Remodelling: Oestrogens

    • Increase OPG to reduce bone resorption.
    • Inhibit osteoclast-recruiting cytokines and counter the bone-resorbing, calcium-mobilising effect of PTH
    • Withdrawal leads to osteoporosis.

    Regulation of Bone Remodelling: Parathyroid Hormone (PTH)

    • Stimulates both bone formation and resorption.
    • Released when blood calcium levels are low.
    • Increases bone resorption to release calcium.
    • Increases calcium reabsorption and phosphate excretion in the kidneys.

    Calcium and Phosphate Metabolism

    • Daily turnover of calcium is 700mg.
    • Concentration of ionized Ca2+ in extracellular fluid and plasma must be tightly controlled.
    • The plasma concentration of Ca2+ is controlled by PTH, calcitriol, and calcitonin.

    Vitamin D

    • Importance in calcium and phosphate metabolism
    • Two types in humans: ergocalciferol (diet) and cholecalciferol (skin).
    • Liver converts cholecalciferol to calcifediol, then to calcitriol in the kidney.
    • Process regulated by PTH and influenced by plasma phosphate.

    Bone Disorders (Osteoporosis, Osteopenia, Osteomalacia, Rickets and Paget's Disease)

    • Osteoporosis is a reduction in bone mass with microarchitecture distortion.
    • Commonest causes include postmenopausal estrogen deficiency and age-related deterioration.
    • Osteopenia is a reduction in mineral content.
    • Osteomalacia and rickets are caused by vitamin D deficiency.
    • Paget's disease involves distorted bone resorption and remodelling processes.

    Non-Pharmacological Treatment

    • Physical activity
    • Healthy habits
    • Dietary recommendations: 100-200mg calcium + proteins, Vitamin A, D, P, K and Mg, Alkaline diet

    Drugs used in Bone Disorders

    • Antiresorptive drugs: Bisphosphonates, Calcitonin, SERMs (Selective estrogen receptor modulators), Denosumab, Vitamin D, Calcium, Calcimimetic compounds.
    • Anabolic agents: PTH, teriparatide.

    Specific Drugs (Bisphosphonates)

    • Inhibit bone resorption mainly by acting on osteoclasts.
    • Should be taken orally on an empty stomach for better absorption.
    • Adverse Effects (ADRs) include gastrointestinal problems, atypical femoral fractures, and osteonecrosis (especially with IV administration).
    • Long-term use should be re-evaluated regularly.

    Specific Drugs (Calcitonin)

    • Thyroid hormone, opposite action of PTH, increases renal excretion of Ca2+.
    • Given by SC or IM or intranasally (less effective).
    • Mechanism of action involves inhibiting osteoclast activity and increasing renal calcium excretion.

    Specific Drugs (Denosumab)

    • Recombinant human monoclonal antibody that inhibits RANKL and mimics OPG.
    • Inhibits osteoclast differentiation.
    • Administered every 6 months.

    Specific Drugs (Romosozumab)

    • Monoclonal antibody that inhibits sclerostin to enhance bone formation, and inhibits osteoclasts.

    Specific Drugs (Vitamin D Analogues)

    • Vitamin D analogues (ergocalciferol, calcifediol, calcitriol)
    • Mechanism involves activating nuclear steroid receptors and increasing Ca2+ absorption, mobilisation from bone, decreasing renal excretion.
    • Clinical use involves deficiency states (rickets, osteomalacia, vitamin D deficiency), hypocalcemia, and osteodystrophy of chronic renal failure.
    • ADRs include excessive intake causing hypercalcemia and elevated phosphate.

    Specific Drugs (Calcium Salts)

    • Calcium salts (e.g. calcium gluconate, lactate, carbonate)
    • Indirect antagonists of PTH
    • Oral administration for dietary deficiency, hypocalcemia, hypoparathyroidism, acute tetany; and calcium carbonate use to treat hyperphosphatemia and prevent/treat osteoporosis
    • ADRs include gastrointestinal disturbance and potential arterial calcification.

    Specific Drugs (Calcimimetic Compounds)

    • Cinacalcet - Enhances parathyroid Ca2+ sensing receptors to decrease PTH secretion, reducing serum Ca levels.

    Specific Drugs (Parathyroid Hormone)

    • Teriparatide (recombinant PTH)
    • Used in low doses intermittently to reverse osteoporosis by stimulating new bone formation, increasing osteoblast numbers and preventing osteoblast apoptosis.
    • Adverse effects include nausea, dizziness, headache, arthralgias, and mild hypercalcemia.. Maximum treatment duration is 24 months.

    Specific Additional information

    • All of these drugs are meant to regulate bone remodeling

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    Lesson 27 - Calcium Homeostasis PDF

    Description

    Test your understanding of bone remodeling and the hormones involved in the process. This quiz covers key concepts such as osteoprotegerin, estrogen effects during menopause, calcium reabsorption, and more. Explore how these elements contribute to bone health and density.

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