Osteoporosis - Marys section
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What is the primary role of 1,25(OH)2D3 in maintaining calcium levels?

  • To increase calcium absorption and reduce excretion in the kidney (correct)
  • To decrease the release of calcium from bone
  • To increase bone mineral density
  • To stimulate the release of parathyroid hormone

    • What is the effect of estrogen deficiency on bone remodeling?

  • It decreases bone resorption and increases bone formation
  • It has no effect on bone remodeling
  • It increases bone formation and has no effect on bone resorption
  • It increases bone resorption and decreases bone formation (correct)

    • What is the effect of calcium and vitamin D supplements on bone mineral density?

  • They have no effect on bone mineral density
  • They significantly increase bone mineral density
  • They slightly reduce the risk of vertebral fractures in postmenopausal women (correct)
  • They decrease bone mineral density

    • What is the primary function of parathyroid hormone in relation to calcium levels?

    <p>To regulate calcium levels by stimulating bone resorption</p> Signup and view all the answers

    What is the effect of hormone replacement therapy (HRT) on bone mineral density in postmenopausal women?

    <p>It increases bone mineral density in a dose-dependent manner</p> Signup and view all the answers

    What is the role of vitamin D in bone health?

    <p>It is essential for bone formation and remodeling</p> Signup and view all the answers

    What is the effect of selective estrogen receptor modulators (SERMs) on bone health?

    <p>They decrease bone resorption and increase bone formation</p> Signup and view all the answers

    What is the importance of peak bone mass in children and adolescents?

    <p>It is essential for achieving optimal bone density and reducing the risk of osteoporosis</p> Signup and view all the answers

    What is the primary function of Parathyroid Hormone (PTH) in calcium homeostasis?

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

    What is the effect of Calcitonin on calcium levels in the plasma?

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

    What is the primary function of osteoclasts in bone turnover?

    <p>To break down and resorb bone tissue</p> Signup and view all the answers

    What is the primary mechanism by which weight resistance training helps to prevent bone deterioration in astronauts?

    <p>By stimulating bone loading and resistance</p> Signup and view all the answers

    What is the normal range of calcium levels in the plasma?

    <p>2.15 to 2.55 mM</p> Signup and view all the answers

    What is the main goal of antiresorptive therapy in the treatment of osteoporosis?

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

    Which of the following is an anabolic therapy for osteoporosis?

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

    What is the role of Vitamin D in bone health?

    <p>It increases bone density and strength</p> Signup and view all the answers

    What is the primary source of calcium in the body?

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

    What is the mechanism by which PTH regulates bone turnover?

    <p>It binds to osteoblasts, which then signal to osteoclasts</p> Signup and view all the answers

    What is the purpose of bone remodeling in the body?

    <p>To accommodate changing mechanical stresses and calcium homeostasis</p> Signup and view all the answers

    What is the role of vitamin D in bone health?

    <p>Regulation of calcium levels in the blood</p> Signup and view all the answers

    What is the consequence of excessive bone resorption?

    <p>Higher risk of fractures</p> Signup and view all the answers

    What is the effect of insufficient dietary intake, intestinal absorption, or kidney reabsorption of calcium on the body?

    <p>It mobilizes calcium from bone by parathyroid hormone (PTH)</p> Signup and view all the answers

    What occurs when the rate of bone deposition is no longer able to match the rate of bone resorption?

    <p>There is a net loss of bone leading to decreased BMD and bone strength</p> Signup and view all the answers

    Which type of therapy targets osteoblasts to increase bone deposition?

    <p>Anabolic therapy</p> Signup and view all the answers

    What is the primary mechanism of action of denosumab in osteoporosis treatment?

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

    What is the result of osteoid mineralization?

    <p>Osteoid returns to normal</p> Signup and view all the answers

    What is the goal of therapeutic approaches to treat osteoporosis?

    <p>To either decrease the rate of bone resorption or increase the rate of bone deposition</p> Signup and view all the answers

    What is the role of osteoblasts in the bone remodeling process?

    <p>To fill cavities with osteoid</p> Signup and view all the answers

    What is a consequence of osteoporosis?

    <p>Decreased bone mineral density and increased risk of fractures</p> Signup and view all the answers

    What is the effect of intermittent treatment with teriparatide (PTH 1-34) on osteoporotic patients?

    <p>Reduces the risk of fractures and stimulates bone turnover</p> Signup and view all the answers

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

    <p>Inhibits the interaction between RANKL and RANK, reducing osteoclast differentiation and bone resorption</p> Signup and view all the answers

    What is the primary difference between etidronate and other bisphosphonates such as alendronate and risedronate?

    <p>Etidronate is less potent and inhibits mineralization, which may cause osteomalacia</p> Signup and view all the answers

    What is the role of RANKL in the regulation of osteoclast activity?

    <p>RANKL is produced by osteoblasts and stimulates osteoclast differentiation and activity</p> Signup and view all the answers

    What is the primary mechanism of action of bisphosphonates in the treatment of osteoporosis?

    <p>Inhibiting osteoclast activity and reducing bone resorption</p> Signup and view all the answers

    What is the primary role of osteoblasts in the regulation of osteoclast activity?

    <p>Osteoblasts produce RANKL, which stimulates osteoclast differentiation and activity</p> Signup and view all the answers

    What is the therapeutic limitation of denosumab in the treatment of osteoporosis?

    <p>It has a limited duration of treatment, typically 2 years</p> Signup and view all the answers

    What is the primary function of parathyroid hormone in relation to calcium levels?

    <p>To stimulate osteoclast activity and release calcium from bone</p> Signup and view all the answers

    What is the consequence of estrogen deficiency on bone remodeling?

    <p>Decreased bone formation and increased bone resorption</p> Signup and view all the answers

    Which of the following is a benefit of hormone replacement therapy (HRT) in postmenopausal women?

    <p>Improved bone mineral density</p> Signup and view all the answers

    What is the primary mechanism of action of selective estrogen receptor modulators (SERMs) on bone health?

    <p>Modulation of estrogen receptor activity</p> Signup and view all the answers

    What is the primary goal of antiresorptive therapy in the treatment of osteoporosis?

    <p>To reduce bone resorption and maintain bone formation</p> Signup and view all the answers

    What is the effect of vitamin D on calcium levels in the body?

    <p>Vitamin D increases calcium levels by reducing excretion</p> Signup and view all the answers

    What is the significance of peak bone mass in children and adolescents?

    <p>It is the maximum amount of bone that can be achieved</p> Signup and view all the answers

    What is the primary regulator of calcium levels in the plasma?

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

    Which cells do not have receptors for Parathyroid hormone (PTH)?

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

    What is the purpose of bone remodeling in the body?

    <p>To accommodate changing mechanical stresses and calcium homeostasis</p> Signup and view all the answers

    What would be the consequence of insufficient dietary intake, intestinal absorption, or kidney reabsorption of calcium?

    <p>Mobilization of calcium from bone by parathyroid hormone</p> Signup and view all the answers

    What is the main goal of antiresorptive therapy in the treatment of osteoporosis?

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

    What is the role of osteoblasts in bone remodeling?

    <p>To form new bone tissue</p> Signup and view all the answers

    Which of the following is NOT a regulator of calcium levels?

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

    What is the result of severe bone deterioration?

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

    Study Notes

    Osteoporosis: Preventative Methods

    • Calcium and vitamin D supplements are recommended to ensure sufficient dietary calcium in adults.
    • Adequate levels of calcium and vitamin D maintain calcium levels, rather than increasing bone mineral density.
    • Calcium and vitamin D may slightly reduce the risk of vertebral fractures in postmenopausal women.
    • In children, peak bone mass is not achieved until 20-22 years, making calcium and vitamin D essential for maximal bone mass.

    Vitamin D Metabolism

    • Vitamin D has multiple forms in the body, with 1,25 Dihydroxy D3 (calcitriol) being the most biologically active form.
    • Vitamin D can be obtained through dietary sources or sunlight conversion, followed by hydroxylation in the liver and kidney.
    • Calcitriol reduces calcium excretion in the kidney and has maximum activity as a nuclear hormone receptor agonist.
    • Calcitriol increases serum calcium by increasing absorption, decreasing elimination, and releasing calcium from bone.

    Osteoporosis: Therapy

    • Hormone Replacement Therapy (HRT) improves Bone Mineral Density (BMD) in postmenopausal women.
    • HRT is associated with costs (increased incidence of uterine cancer, breast cancer, and venous thromboembolisms) and benefits (increased BMD and improved menopause symptoms).

    Antiresorptive Therapy: HRT

    • Estrogen deficiency results in increased bone remodeling, favoring resorption through increased osteoclast activity.
    • Estrogen deficiency increases cytokine levels (IL-1, IL-6, and TNF), which favor osteoclast formation.
    • HRT (estrogen) increases BMD in a dose-dependent manner.

    Antiresorptive Therapy: SERMS

    • Selective Estrogen Receptor Modulators (SERMs) are concerned with bone loading and weight resistance training.
    • SERMs are important for astronauts to prevent severe bone deterioration.

    Calcium Homeostasis

    • Circulating calcium levels are between 2.15 and 2.55 mM or 8.7 to 10.3 mg/dL.
    • Calcium levels are controlled by parathyroid hormone (PTH), vitamin D, and calcitonin.
    • Calcium levels are affected by dietary intake, GI absorption, and renal clearance.

    Key Regulator: PTH

    • PTH increases circulating calcium levels by signaling osteoblasts to stimulate osteoclast activity.
    • PTH is essential for maintaining calcium homeostasis and bone remodeling.

    Overview: Bone Turnover

    • Bone turnover involves growth and resorption throughout life, accommodating mechanical stresses and calcium homeostasis.
    • The process of bone remodeling is under the control of local growth factors and endocrine factors, including PTH.

    Bone Turnover

    • Osteoid is a collagen-rich matrix that becomes mineralized and returns to normal
    • Osteoblasts on the surface of bone produce osteoid, which then gets mineralized
    • Osteoclasts on the surface of bone resorb old bone, leading to a net loss of bone

    Osteoporosis

    • Osteoporosis occurs when the rate of bone deposition is no longer able to match the rate of bone resorption, leading to a net loss of bone and decreased bone mineral density (BMD) and bone strength
    • Therapeutic approaches to treat osteoporosis aim to either decrease bone resorption (anti-resorptive therapies) or increase bone deposition (anabolic therapies)

    Osteoporosis Treatment

    • Anti-resorptive therapies target osteoclasts to decrease bone resorption
    • Anabolic therapies target osteoblasts to increase bone deposition
    • Examples of anti-resorptive therapies include hormone replacement therapy (HRT), selective estrogen receptor modulators (SERMs), bisphosphonates, and denosumab
    • Examples of anabolic therapies include parathyroid hormone (PTH) and sclerostin antibodies

    Prevention Methods

    • In adults, calcium and vitamin D supplements are recommended to ensure sufficient dietary calcium and vitamin D levels
    • Calcium and vitamin D supplements do little to increase bone mineral density but ensure adequate levels of calcium and prevent the release of parathyroid hormone (PTH)
    • Calcium and vitamin D supplements may slightly reduce the risk of vertebral fractures in postmenopausal women
    • In children, peak bone mass is not achieved until 20-22 years, and calcium and vitamin D are essential for maximal bone mass

    Vitamin D Metabolism

    • Vitamin D has multiple forms in the body, with the most biologically active form being 1,25-dihydroxy D3 (calcitriol)
    • Vitamin D can be obtained through dietary sources or conversion of precursors by sunlight, followed by hydroxylation in the liver and kidney
    • Calcitriol has maximum activity in increasing serum calcium levels by increasing absorption, decreasing elimination, and increasing release from bone
    • Calcitriol has high-affinity receptors in the intestine and kidneys

    Antiresorptive Therapy: HRT

    • Hormone replacement therapy (HRT) improves bone mineral density (BMD) all over the body in postmenopausal women
    • HRT is associated with costs and benefits, including increased incidence of uterine cancer and breast cancer, and increased risk of cardiovascular events
    • Estrogen deficiency results in increased bone remodeling, favoring resorption, mostly through increased osteoclast activity
    • HRT (estrogen) increases BMD in a dose-dependent manner

    Antiresorptive Therapy: SERMs

    • Selective estrogen receptor modulators (SERMs) are examples of anti-resorptive therapies
    • Examples of SERMs include etidronate and nitrogen-containing analogues, such as alendronate and risedronate

    Antiresorptive Therapy: Bisphosphonates

    • Bisphosphonates are examples of anti-resorptive therapies
    • Examples of bisphosphonates include etidronate, alendronate, and risedronate
    • Etidronate is a first-generation bisphosphonate, less potent than subsequent generations, and well-tolerated
    • Alendronate and risedronate are administered continuously, well-tolerated, and reduce the risk of vertebral fractures and fractures of the spine, hip, and wrist

    Antiresorptive Therapy: Denosumab

    • Denosumab is a human monoclonal antibody to RANKL, which inhibits osteoclast differentiation and reduces bone resorption
    • RANK is expressed on the surface of osteoclast precursors, and RANKL is expressed on the surface of osteoblasts
    • Denosumab reduces osteoclast differentiation and activity by inhibiting the interaction between RANK and RANKL

    Anabolic Therapies: PTH

    • Parathyroid hormone (PTH) is secreted from the parathyroid glands in response to low serum calcium levels
    • PTH acts in the kidney to stimulate calcium reabsorption and in bone to stimulate bone resorption, releasing stored calcium
    • Intermittent treatment with teriparatide (PTH 1-34) stimulates bone turnover and reduces the risk of fractures in osteoporotic patients

    Novel Anabolic Therapy: Sclerostin Antibodies

    • Sclerostin antibodies are novel anabolic therapies that stimulate bone deposition
    • Sclerostin antibodies work by inhibiting the sclerostin protein, which regulates bone formation and resorption

    Calcium Homeostasis

    • Circulating calcium levels in the plasma are between 2.15 and 2.55 mM or 8.7 to 10.3 mg/dL
    • Calcium levels are controlled by parathyroid hormone (PTH), vitamin D, and calcitonin
    • Calcium levels are affected by dietary intake, GI absorption, renal clearance, and bone absorption and release

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