Calcium Homeostasis and Whole Body Handling
42 Questions
3 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of 1,25-dihydroxyvitamin D in the body?

  • To enhance bone formation and growth
  • To increase calcium absorption in the kidneys
  • To stimulate the production of cytokines
  • To maintain homeostasis of calcium levels (correct)
  • How does parathyroid hormone (PTH) affect calcium reabsorption in the kidneys?

  • By increasing activity of calcium channels and pumps (correct)
  • By stimulating osteoblast proliferation
  • By decreasing the activity of calcium channels
  • By increasing the synthesis of calcitriol
  • Which hormone is primarily involved in the regulation of second hydroxylation of vitamin D?

  • Insulin
  • Glucagon
  • Thyroid hormone
  • Prolactin (correct)
  • What could be a potential symptom of hypocalcemia?

    <p>Muscle weakness</p> Signup and view all the answers

    What is one possible effect of hypercalcemia on the body?

    <p>Decreased heart rate</p> Signup and view all the answers

    What is the primary role of calcitonin in the body?

    <p>Reduce bone turnover and calcium release</p> Signup and view all the answers

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

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

    What condition is indicated by total serum calcium levels exceeding 2.62 mmol l-1?

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

    Which of the following symptoms is commonly associated with hypocalcaemia?

    <p>Pins and needles</p> Signup and view all the answers

    Which hormone mimics the action of PTH and is involved in calcium homeostasis?

    <p>Parathyroid hormone-related protein (PTHrP)</p> Signup and view all the answers

    What triggers the secretion of fibroblast growth factor 23 (FGF23)?

    <p>Increased plasma phosphate concentrations</p> Signup and view all the answers

    What is a common mnemonic symptom associated with hypercalcaemia?

    <p>Bones, stones, groans, and psychiatric overtones</p> Signup and view all the answers

    Which hormones primarily influence bone turnover aside from PTH?

    <p>Oestrogen and glucocorticoids</p> Signup and view all the answers

    What is primarily responsible for regulating calcium concentrations in the body?

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

    What condition can result from a lack of production of parathyroid hormone (PTH)?

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

    Which of the following is NOT a symptom of hypoparathyroidism?

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

    What is one potential effect of hyperparathyroidism on the body?

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

    Which vitamin D metabolite plays a critical role in calcium homeostasis?

    <p>1,25-dihydroxyvitamin D</p> Signup and view all the answers

    How does chronic kidney disease primarily affect calcium regulation?

    <p>It leads to a deficiency of 1,25-dihydroxyvitamin D</p> Signup and view all the answers

    What can excessively high levels of calcium in the blood lead to?

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

    Which symptom is commonly associated with hypocalcaemia?

    <p>Muscle spasms</p> Signup and view all the answers

    What role do sex hormones play in calcium regulation?

    <p>Influence calcium homeostasis</p> Signup and view all the answers

    What is a primary physiological role of vitamin D in calcium metabolism?

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

    Which hormone is primarily responsible for increasing blood calcium levels?

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

    What is a common symptom of hypocalcaemia?

    <p>Tingling or numbness in fingers</p> Signup and view all the answers

    How does calcitonin affect calcium levels in the body?

    <p>Reduces bone resorption of calcium</p> Signup and view all the answers

    What is an effect of hypercalcaemia on the neuromuscular system?

    <p>Decreased muscle contraction strength</p> Signup and view all the answers

    Which factor plays a role in the regulation of calcium reabsorption in the kidneys?

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

    What is typically associated with hyperparathyroidism?

    <p>Brittle bone structure</p> Signup and view all the answers

    Which mechanism does vitamin D primarily use to exert its effects on its target cells?

    <p>Modulation of gene expression</p> Signup and view all the answers

    Which symptom is commonly associated with chronic hypercalcaemia?

    <p>Abdominal pain</p> Signup and view all the answers

    Which of the following hormones directly inhibits the release of calcium from bones?

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

    Which hormones are primarily involved in calcium homeostasis in the body?

    <p>Parathyroid hormone, Calcitonin, Vitamin D metabolites</p> Signup and view all the answers

    What is the physiological role of inorganic phosphate (Pi)?

    <p>Aids in cellular signaling and formation of ATP</p> Signup and view all the answers

    What would likely occur in the body with a deficiency of parathyroid hormone (PTH)?

    <p>Decreased calcium resorption from bones</p> Signup and view all the answers

    What is a major symptom of hypocalcaemia?

    <p>Numbness and tingling in fingers</p> Signup and view all the answers

    Which process is primarily responsible for calcium reabsorption in the kidneys?

    <p>Hormonal regulation</p> Signup and view all the answers

    What effect does hypercalcaemia have on calcium-sensing receptors (CaSR)?

    <p>They are unresponsive, leading to decreased secretion of hormones</p> Signup and view all the answers

    What is the role of 1,25-dihydroxyvitamin D in calcium homeostasis?

    <p>It enhances intestinal absorption of calcium</p> Signup and view all the answers

    How do calcium-sensing receptors (CaSR) contribute to cellular functions?

    <p>Modulate enzyme secretion and signaling</p> Signup and view all the answers

    Which statement accurately describes calcium resorption from bones?

    <p>It is stimulated by parathyroid hormone</p> Signup and view all the answers

    PTH receptors are expressed on which of the following cellular locations?

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

    Study Notes

    Calcium Homeostasis

    • Calcium (and phosphate) are vital for skeletal and tooth formation, biochemical pathways, and signalling cascades.
    • Calcium plays a role in skeletal rigidity, connective tissue, teeth, blood clotting (intrinsic/extrinsic cascades), muscle (excitation-contraction coupling), neurotransmission (stimulus-secretion coupling), and cell adhesion (cadherins).
    • Calcium also acts as a second messenger for enzymatic activity (e.g., calmodulin).

    Whole Body Calcium Handling

    • Ionised calcium is the biologically active form.
    • Total calcium concentration ranges from 2.1-2.8 mmol/L.
    • Ionised calcium accounts for roughly 50% of the total.
    • Most calcium is protein-bound (approximately 45%), which is inactive and not excreted.
    • The remaining calcium is complexed with phosphate, bicarbonate, or citrate (approximately 5%).
    • Dietary calcium intake plus calcium resorbed from bone equals calcium lost in faeces, sweat, and saliva, plus calcium deposited in the bone.

    Inorganic Phosphate (Pi)

    • Inorganic phosphate plays a role in bone formation (hydroxyapatite and hydroxyapatite crystals) and ATP formation.
    • It is also a component of nucleotides, nucleosides, and phospholipids.
    • Inorganic phosphate is involved in cellular signalling.
    • Normal plasma inorganic phosphate concentration is 2.3 mmol/L.
    • Inorganic phosphate exists primarily as HPO42- or H2PO4-.

    Calcium Homeostasis Hormones

    • Calcium homeostasis is maintained by three hormones that act on bone, kidney, and intestines.
    • These hormones include:
      • Metabolites of vitamin D (1,25-dihydroxyvitamin D
      • Parathyroid hormone (PTH)
      • Calcitonin

    Parathyroid Hormone (PTH)

    • Manufactured in parathyroid chief cells.
    • Biologically active peptide of 84 amino acids.
    • PTH is involved in calcium homeostasis.
    • PTH is involved in stimulating the recruitment of osteoblasts, which promote osteoclast activity.
    • PTH stimulates Vitamin D synthesis resulting in increased calcium absorption from the gut.
    • In kidneys PTH increases calcium reabsorption.
    • Hypocalcaemia stimulates PTH secretion.
    • Heterozygous CaSR inactivating mutation causes FHH (familial hypercalcemic hypocalciuria).
    • Heterozygous CaSR and Ga11 gain-of-function mutation causes high urinary excretion of calcium in normal plasma calcium.

    Calcium-Sensing Receptors (CaSR)

    • GPCR which responds to numerous ligands.
    • CaSRs mediate multiple physiological effects, including calcium homeostasis, nutrient sensing (parietal and G cells), and enzyme secretion ( alpha and beta cells).
    • CaSRs are involved in regulating PTH secretion.

    Vitamin D Metabolites (1,25-Dihydroxyvitamin D)

    • Vitamin D, particularly its active form 1,25-dihydroxyvitamin D (calcitriol), is critical for calcium homeostasis.
    • Vitamin D metabolites promote calcium absorption in the small intestine.
    • Vitamin D metabolites stimulate sodium and phosphate co-transporters in the kidneys resulting in increased calcium reabsorption.
    • Vitamin D metabolites increase osteoclast numbers.
    • Vitamin D production is influenced by growth hormone, prolactin, and oestrogen.
    • FGF23 reduces 1,25-dihydroxyvitamin D levels.

    Calcitonin

    • Produced in the thyroid gland (clear cells).
    • Biologically active peptide of 32 amino acids.
    • Calcitonin antagonises PTH's action on bone.
    • Calcitonin reduces osteoclast activity, resulting in less calcium released from bone. Calcitonin reduces the bone turnover rate.

    Other Hormones

    • Sex hormones (e.g., oestrogen, testosterone) impact bone turnover.
    • Glucocorticoids also influence bone density.
    • PTHrP mimics PTH's action on bone and kidney.

    Inorganic Phosphate Homeostasis

    • FGF23 plays a key role in regulating inorganic phosphate concentrations.
    • Increased plasma phosphate levels stimulate FGF23 production.
    • PTH and calcitriol influence phosphate release from bone and renal excretion.

    Hypocalcemia

    • Low plasma Ca2+
    • Clinical presentation: Pins and needles, muscle spasms (tetany), paralysis, convulsions
    • Total plasma serum calcium < 0.5 mmol/l
    • Ionised plasma serum calcium < 0.3 mmol/l

    Hypercalcemia

    • High plasma Ca2+
    • Clinical presentation: Lethargy, depression, constipation, Renal calculi, frequent urination, Nausea, arrhythmias
    • Total plasma serum calcium > 2.62 mmol/l
    • Ionised plasma serum calcium > 1.31 mmol/l

    Hypoparathyroidism

    • Characterised by lack of PTH production or defects in responsiveness to PTH.
    • Symptoms: Muscle spasms (tetany), hypocalcaemia, hyperphosphatemia

    Hyperparathyroidism

    • Characterised by excess PTH.
    • Can be primary (tumours) or secondary (chronic kidney disease, vitamin D deficiency).
    • Symptoms: Hypertension, constipation, weakness, confusion, hypercalcaemia.

    Vitamin D Deficiency

    • Mild Deficiency: Increased PTH, high bone turnover.
    • Moderate Deficiency: reduced bone density, increased bone turnover, increased risk of hip fracture.
    • Severe Deficiency: osteomalacia, rickets in children.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Description

    This quiz explores the vital roles of calcium and phosphate in the body, including their importance for skeletal formation, biochemical pathways, and signalling. It also covers the mechanisms of calcium handling and its various forms in the body, providing a comprehensive overview of calcium's physiological functions.

    More Like This

    Calcium and Bone Health Quiz
    24 questions
    Calcium and Its Functions
    37 questions

    Calcium and Its Functions

    FreeChrysoprase6849 avatar
    FreeChrysoprase6849
    Calcium Homeostasis & Functions Quiz
    24 questions
    Use Quizgecko on...
    Browser
    Browser