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Physiology final exam > Topic 71 - The role of the PTH, calcitonin, and the D-hormone in the Ca balance > Flashcards

Topic 71 - The role of the PTH, calcitonin, and the D-hormone in the Ca balance Flashcards

1
Q

Words to include in the role of PTH in the Ca balance

A

PTH: Parathryoid hormone

  • Bone formation
  • Resorption
  • Regulation of plasma calcium level
  • Parathyroid gland

PTH regulation

  • Serum calcium levels determine secretion
  • Direct regulation:
    • Plasma calcium levels ↓ → PTH synthesis & secretion stimulated
    • Plasma calcium levels ↑ → PTH synthesis & secretion inhibited

PTH synthesis

  • Pre-pro-parathormone
    • 115 amino acid long pepetide
    • Chief cells (location)
  • Pro-PTH cleaved
  • PTH cleaved
  • PTH
    • Dissociated from carboxyl-terminal fragment → blood stream

PTH action

  • PTH increases calcium levels
    • Direct actions
    • Indirect actions
  • Bone
    • Facilitation of glycolysis
    • Inhibition of bone formation
    • Ca premability ↑ (osteoclast)
    • Osteolysis ↑
      • Direct & indirect effect on osteoclast
  • Kidney
    • Ca resorption ↑
    • P excretion ↑
    • D-hormone synthesis ↑
      • 1-hydroxylase
  • Mammary gland
    • Excreted calcium in milk ↓
  • Intestines
    • Ø direct action on calcium absorption
      • Acts through enhancement of renal D-hormone synthesis

PTH overproduction

  • Cancerous transformation
    • Chief cells shunting out uncontrolled amounts of PTH
  • Demineralization of bone
    • Soft bone
    • Rubber jaw syndrome

PTH deficiency

  • Removal of parathyroid gland
    • Calcium level ↓ → death
  • Symptoms:
    • ​Excitability of muscular and neural tissues ↑
    • Hyperactive reflexes
    • Tetanic spasms
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2
Q

Words to include in the role of calcitonine in the Ca balance

A
  • Peptide hormone
  • Parfollicular cells (produces_)_
  • Plasma Ca level:
    • Plasma calcium ↑ → enchaced calcitonin secretion
    • Plasma calcium ↓ → enchaced PTH secretion

CT synthes__is

  • Plasma clacium levels ↑ → CT synthesis & release
  • Action: Plasma calcium ↓

CT regulation

  • Rapid blood calcium increase can not exceed calcium resorptive capacity of the kidney
    • No calcium lost

Feed-forward mechanism

  • Foodstuff: calcium intake → gastrin secretion ↑ → C-cells: CT secretion ↑ → Plasma: calcium concentration ↑
  • CT level ↑
    • Ø gastrin secretion
    • Negative feedback

CT action

  • CT decrease serum calcium level by acting on:
    • ​Bone
      • Osteoclast activity inhibited
        • Bone formation facilitated
      • Osteoclast inhibition of Ca-pump & permability ↓
        • D-hormone activated Ca-pump (ø)
        • Ca transprot from bone to blood (ø)
        • Ca deposition enhanced
        • Plasma Ca level ↓
    • Kidney
      • Ca resorption ↓
      • P excretion ↑
      • D-hormone synthesis ↓
        • 1-α-hydroxylase inhibition

CT overproduction

  • No disturbance in Ca metabolism

CT deficiency

  • Removal of thyroid gland → plasma CT ↓
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3
Q

Words to include in the role of D-hormone in the Ca balance

A
  • Vitamin-D → D-hormone

Role

  • Maintains balance of bone formation and resorption

D-hormone action

  • Bone
    • Facilitation of osteolysis
      • Ca-pump activity ↑
    • Facilitation of bone formation
  • Kidney
    • Tubular resorption of Ca ↑
    • Phosphorus reabsorption ↑
      • Anti-PTH effect
  • Intestines
    • Ca binding protein (CaBP)
      • Ca reabsorption ↑

D-hormone deficiency

  • Ø UV-light
  • 1-α-hydroxylase
    • Genetic lack
  • Young: alterations of normal developments
    • Rachitis
  • Adult: soft bone
    • Osteomalatia
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4
Q

Topics to include in the essay

A
  1. PTH
    • Role of PTH
    • Synthesis of PTH
    • Regulation of PTH
    • PTH action
      • Bone
      • Kidney
      • Mammary gland
      • Intestines
    • PTH overproduction
    • PTH deficiency
  2. D-hormone
    • Role of D-hormone
    • D-hormone action
      • Bone
      • Kidney
      • Intestines
    • D-hormone deficiency
  3. Calcitonine
    • Origin of CT
    • CT regulation
    • Feed-forward mechanism
    • CT action
      • Bone
      • Kidney
    • CT overproduction
    • CT deficiency
  4. Hormonal regulation of:
    • PTH
    • D3
    • CT
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5
Q

PTH

  1. Role of PTH
  2. Synthesis of PTH
  3. Regulation of PTH secretion
  4. PTH action
  5. PTH overproduction
  6. PTH deficiency
A
  • PTH: Parathyroid hormone​
  • Produced by the parathyrid gland

1. Role of PTH

  • Important in bone formation and resorption
    • ​Important in the regulation of plasma calcium level

2. Synthesis of PTH

  • Pre-pro-parathormone is a 155 amino acid long peptide
    • Stored in chief cells
  • Pro-PTH and PTH are cleaved off drom it
  • PTH, having dissociated from the carboxyl-terminal fragments.gets into the blood stream

3. Regulation of PTH secretion

  • Secretion is determined by serum calcium levels
  • Direct regulation:
    • Calicum level ↓ → PTH synthesis & secretion
    • Calcium level ↑ → Inhibits PTH synthesis & secretion

4. PTH action

  • PTH increases calcium level through direct and indirect actions:
    • ​Bone:
      • ​Facilitation of glycloysis in cells around the bone
      • Ø bone formation
      • Ca permability ↑ (osteoclast)
      • Osteolysis ↑
    • Kidney:
      • _​_Ca resorption ↑
      • P excretion ↑
      • D-hormone synthesis ↑ (1-hydroxylase)
    • Mammary gland:
      • ​Decreases the amount of excreted Ca in milk
    • Intestines:
      • ​Does not act directly on Ca absorption
        • Acts through the enhancement of renal D-hormone synthesis

5. PTH overproduction

  • A result of cancerous transformation of chief cells churning out uncorntrolled amounts of PTH
  • A result of chronically low Ca supply by the feed
    • Demineralization of bone → soft bone (rubber jaw syndrome)

6. PTH deficiency

  • Removal of parathyroid gland → blood Ca level ↓ → death
  • Symptoms of PTH deficiency:
    • Excitability of muscular and neural tissues increases
    • Hyperactive reflexes
    • Tetanic spasms
  • Cause of deficiency:
    • Parathyroidectomy
      • ​Accidental surgical removal of parathyroid gland
    • Auto-immune atrophy
    • Lack of PTH receptors
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6
Q

Calcitonin (CT)

  1. CT synthesis
  2. CT regulation
  3. CT action
  4. CT overproduction
  5. CT deficiency
A
  • Peptide hormone
    • ​32 amino acids
  • Produced by parafollicular cells embedded in the thyroid tissue

1. CT synthesis

  • CT is synthesized and released when plasma Ca level ↑
    • ​Action: drastic reduction in plasma Ca

Figure: feed-forward mechanism

2. Regulation of CT

  • Regulation of secretion:
    • Plasma Ca level
    • Feed-forward mechanism
  • CT is released to the signal of high plasma Ca level
  • Feed-forward mechanism activated CT synthesis via gastrin
    • ​Ensures presence of CT in the plasma by the time of extensive Ca absorption
  • Rapid blood Ca increase can not exceed Ca resorptive capacity of the kidney → No Ca will be lost

Feed-forward mechanism

  • See figure
  • Increased CT level inhibits gastrin secretion
    • ​Negative feedback

4. CT aciton

  • Action: drastic reduction of plasma Ca
    • ​Acts as an antagonist of parathyroid hormone
  • Acts on:
    • Bone:
      • ​Inhibition of osteoclast activity
        • ​Facilitates bone formation
      • Osteoblast inhibition of Ca-pump and decrease permability
        • Inhibiton of D-hormone activated Ca-pump
        • Ø Ca transport from bone → blood
        • Ca deposition ↑
        • Plasma Ca level ↓
    • Kidney:
      • _​_Ca resorption ↓
      • P excretion ↑ (synergism with PTH)
      • D-hormone synthesis ↓ (​1-α-hydroxylase inhibition)

4. CT overproduction

  • No disturbance in Ca metabolism

5. CT deficiency

  • Removal of thyroid gland → plasma CT ↓ (some times)
    • CT never disappear entirely, as other tissues produce CT
  • Not dangerous
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7
Q

D-hormone

  1. D-hormone role
  2. D-hormone action
  3. D-hormone deficiency
A
  • Vitamin-D → D-hormone
  • Steroid hormone
  • Lipid soluble
    • ​Transported in plasma bound to transcalciferin (specific globulin)
  • Cholesterol → cholecalciferol → 25-OH-D3 → 1-α-hydroxylase → D-hormone (1,25-dihydroxy-cholecalciferol)

1. D-hormone role

  • The active hormone maintains the balance of bone formation and resorption

2. D-hormone action

  • D-hormone influences Ca metabolism of the:
    • Bone:
      • ​Facilitation of osteolysis
        • ​Ca-pump activity ↑
      • Facilitation of bone formation
    • Kidney:
      • ​Tubular resorptionofCa ↑
      • Phosphorous reabsorption ↑
        • ​Anti PTH effect
    • Intestines:
      • _​_Ca Binding Protein (CaBP): Ca reabsorption ↑

3. D-hormone deficiency

  • Ø UV-light
  • Genetic lack of 1-α-hydroxylase
  • Young: alterations of normal development
    • Rachitis
  • Adults: Soft bone
    • ​Osteomalatia
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8
Q

Hormonal regulation

Fill out the table

A
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9
Q
  1. Name the hormones facilitating oseogeneiss
  2. Name the hormones inhibitng osteogenesis
A
  1. Hormones facilitating osteogenesis:
    1. Parathyroid hormone
    2. Calcitonin
    3. Growth hormone (via somatomedin)
    4. Thyroid hormones
    5. Estrogens
    6. Insulin
    7. Gastin
  2. Hormones inhibiting osteogenesis:
    1. Glucocorticoids
    2. Prostaglandin-E
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Physiology final exam (111 decks)

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