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MEH Sem 1 > Lecture 14 - Calcium metabolism > Flashcards

Lecture 14 - Calcium metabolism Flashcards

1
Q

What is the parathyroid gland formed from embryologically?

A

Third and fourth brachial artery

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2
Q

Where and how many PTH glands?

A
  • Behind thyroid glands

- x4

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3
Q

What are some importance of calcium?

A
  • Hormone secretion (insulin)
  • Muscle contraction
  • Nerve conduction
  • Exocytosis
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4
Q

How is calcium vital for bone formation?

A

Ca+K: Hydroxyapatite crystals, a major component of bone

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5
Q

What regulates Ca conc. in blood?

A
  • PTH + calcitriol
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6
Q

How does PTH affect calcium and K homeostasis?

A
  • PTH ⬆️, K ⬇️
  • ⬆️Ca reabsorption from kidney
  • ⬆️osteoclast resoption –> increase bone turnover
  • ⬆️absorption of Ca from food (small intestine)
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7
Q

What types of Vit. D are present in the diet?

A
  • Ergocalciferol (D2): obtain from mushrooms (less potent version of vit D
  • Cholecalciferol (D3): Liver of fatty fish
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8
Q

How does Vit D act in Ca & K homeostasis?

A
  • Decrease PTH production
  • ⬆️Ca reabsorption from kidney
  • ⬆️mineralisation of Ca to bone
  • ⬆️absorption of Ca and K from food (small intestine)
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9
Q

What parameters define hypercalcaemia?

A
  • Serum calcium >2.51mmol/L

>3 is severe

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10
Q

What are some symptoms of hypercalcaemia?

A
  • Moans –> Constipation
  • Bones –> bone aches
  • Stones –> Kidney stones
  • Groans –> Confusion
  • Thirst and polyuria
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11
Q

What indication does high calcium and low PTH show?

N.B PTH can drive hypercalcaemia

A
  • High Ca due to diff factor (not PTH from parathyroid gland)
  • Most likely= cancer –> produce PTH like peptide
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12
Q

What are some examples of cancers with high calcium?

A
  • Myeloma (blood cancer)

- Bone metastases (Bronchus, Thyroid, Breast, Kidney)

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13
Q

Other than cancers what can be a cause of high Ca and low PTH?

A
  • TB
  • Sarcoidosis: growth of tiny cancers in lung
  • Granulomas that secrete calcitriol
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14
Q

What does high Ca and high PTH suggest?

A
  • Not cancer

- Primary hyperparathyroidism: benign parathyroid adenoma

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15
Q

What are the effects of primary hyperparathyroidism?

A
  • High Ca, Low K

- ⬆️bone turnover

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16
Q

What is the treatment for acute severe hypercalcaemia (medical emergency–> SEVERE DEHYDRATION)?

A
  • Fluid into veins (normal saline 0.9%)

- Treat underlying cause

17
Q

What are the parameters of hypocalcaemia?

A
  • Serum Ca <1.9mmol/L

- Symptoms severe if sudden drop

18
Q

What does hypocalcaemia result in?

A
  • Hyperexcitability of NS (neuromuscular junction)

- Leads to paraesthesia (pins & needles), tetany (involuntary muscle contraction), paralysis, convulsions

19
Q

What are some causes of hypocalcaemia?

A
  • Vit D deficiency

- Hypoparathyroidism

20
Q

How does low vit D result in secondary hyper-PTH?

A
  • Low Vit D –> low Ca/K –> High PTH

- Stimulation of Ca sensing receptors reduces PTH

21
Q

What are some causes of Vit D deficiency? And what does it result in adults or children if severe?

A
  • Lack of sunlight
  • Dietary deficiency
  • GI disease
  • Kidney disease
  • Pigmented or covered skin
  • Result in rickets in children, osteomalacia in adults
22
Q

What is the diff. btw osteoporosis and osteomalacia?

A
  • Osteomalacia = normal structure of bone but under mineralised
  • Osteoporosis= structurally degraded but fully mineralised
23
Q

What does osteomalacia result in?

Low Ca

A
  • Gluteal muscle weakness leads to waddling gait (bend legs)

- Multiple fractures

24
Q

What is the levels of substances in hypo-PTH?

A
  • Low Ca & PTH

- High K

25
Q

What are some causes of hypo-PTH?

look out for scar in neck

A
  • Surgical removal/damage of PTH gland
  • Pathology of PTH gland
  • Failure of 3rd or 4th brachial artery
26
Q

How to treat acute severe hypo-PTH?

a med emergency

A
  • Assess airway and conscious level
  • ECG monitor for heart
  • Intravenous Ca and monitoring
27
Q

List some risk factors for osteoporosis.

A
  • Menopausal women
  • Smoking and immobile
  • Endocrine disease (hypo-PTH)
  • Family history
28
Q

What are some sources of Ca?

A
  • Diet (Dairy products major source)= 800-1200mg per day
  • Intestine net uptake is 175mg/day (same as Ca excreted in urine)
  • Bone calcium deposition (controlled by K) is 280mg/day
  • Kidney reabsorb Ca
29
Q

How is free Ca (biologically active) measured?

A
  • Total Ca measured: Free ionised/ Bound to albumin/ Bound to low-molecular weight organic anions (citrate)
  • Levels adjusted depending on albumin
30
Q

What are effects of PTHrP?

related peptide

A
  • Increase Ca release from bone
  • Reduce renal Ca excretion
  • Reduce renal absorption
  • X increase renal C-1 hydroxylase –> calcitriol X increase
31
Q

How much Ca in body?

A
  • 1kg
  • Vast majority of this present in the skeleton and teeth. Soft tissues contain about 10g of calcium and approx 1g is present in the extracellular fluid.
32
Q

How many PTH glands are there in a human body?

A

4

33
Q

What type of hormone is PTH?

A

Peptide hormone

34
Q

How does PTH exert its effects on the GI tract?

A
  • Indirectly through promoting the formation of calcitriol
35
Q

How do principal cells in these glands sense plasma calcium concentration?

A

GPCR activated by calcium

MEH Sem 1 (18 decks)

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