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CC 138 - Monoarthritis > Calcium Homeostasis > Flashcards

Calcium Homeostasis Flashcards

1
Q

The main roles of Calcium are?

A

Muscle contractions, neurotransmitter release, calcification of bones and teeth, cell adhesion, blood clotting and excitation (contraction coupling)

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2
Q

How is Calcium in the body regulated?

A

Via principle organ systems (gut, bones and kidneys) and via hormones (PTH, Vit D3 and Calcitonin)

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3
Q

PTH, Vitamin D3 and Calcitonin regulate what in the body?

A

Calcium levels

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4
Q

What is a hormone?

A

An agent that is released at one site, diffuses systemically and acts at another site.

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5
Q

What is the Vitamin D3 precursor (it’s in your skin!)?

A

7-dehydrocholesterol

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6
Q

What catalyses the activation of Vitamin D3?

A

UV light

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7
Q

What is detected in the blood to find the levels of Vitamin D3?

A

25-hydroxy D3

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8
Q

Calcitriol is another term for what?

A

1,25-dihydroxyvitamin D3 - the active form of Vitamin D3

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9
Q

What are our main sources of Vitamin D3?

A

Diet, self generated & supplements

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10
Q

Self generated Vitamin D3 isn’t toxic, but supplements are in high doses, why is this?

A

Supplements aren’t the activated form and therefore aren’t excreted like the self generated form via the urine and faeces.

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11
Q

Which hormone takes longer to act; a nuclear hormone or a peptide hormone?

A

Nuclear hormones take longer!

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12
Q

How does vitamin D3 help regulate Calcium levels?

A

Stimulates the gut to take up serum calcium and directly stimulates the terminal differentiation of osteoclasts and activates osteoblasts in bones to increase serum calcium uptake.

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13
Q

What does PTH stand for?

A

Parathyriod hormone

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14
Q

What is the role of PTH in maintaining calcium levels?

A

PTH stimulates bone resorption of serum calcium, renal tubular reabsorption of Ca2+ and stimulates renal 1α-hydroxylation of 25(OH)vitamin D3  indirectly  intestinal absorption of Ca2+ and therefore serum Ca2+

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15
Q

I’m a 32 amino acid peptide and I’m synthesised by the parafollicular cells of the thyriod gland (C-cells). What am I?

A

Calcitonin

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16
Q

What is the role of Calcitonin in Calcium homeostasis?

A

Calcitonin has no role in normal day to day Calcium homeostasis.

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17
Q

What is the term for high calcium levels?

A

Hypercalcaemia

18
Q

What are the main symptoms of hypercalcaemia?

A

Altered mental state, lethargy, depression. Decreased gut motility, diuresis and impaired renal concentrating ability. Fractures, shortened QT interval and exacerbation of hypertension.

19
Q

Hypercalcaemia is a risk factor for which common kidney pathology?

A

Kidney Stones.

20
Q

How is PTH controlled?

A

Negative feedback loop - when Ca levels rise, PTH self inhibits its own transcription.

21
Q

What regulates the thyriod gland’s production of Calcitonin?

A

Serum Ca levels

22
Q

In stress situations the role of calcitonin is thought to be what?

A

Decreasing bone resorption when plasma Ca is high

23
Q

Stimulation of PTH, increase in bone resorption of CA and increased 1,25(OH)2 D3 production suggests what?

A

Falling Blood Calcium

24
Q

What happens when blood calcium increases?

A

Down regulation of PTH, decreased bone resorption, increase in urinary Ca loss and a decrease in 1,25(OH)2 D3 production.

25
Q

The following are indications of what?

• Stones (renal or biliary)
• Bones (bone pain)
• Groans (abdominal pain, nausea and vomiting)
• Thrones (polyuria)
• Psychiatric overtones (Depression 30–40%,
anxiety, cognitive dysfunction, insomnia, coma)

A

Hypercalcaemia

26
Q

What hormonal changes can cause hypercalcaemia?

A

Hormonal changes such as: primary hyperthyriodism, hypervitaminosis D or paraneoplastic changes.

27
Q

What are the non-hormonal changes that cause hypercalcaemia?

A

Renal failure, milk alkali syndrome, thiazides/litium/other drugs or Cestrum diurnum ( a plant).

28
Q

What is milk alkali syndrome?

A

Milk-alkali syndrome is characterized by high blood calcium caused by taking in too much calcium and absorbable alkali; common sources of calcium and alkali are dietary supplements taken to prevent osteoporosis and antacids. If untreated, milk-alkali syndrome may lead to kidney failure or death.

29
Q

What is the term for low blood calcium levels?

A

Hypocalcaemia

30
Q

At what blood calcium level does hypocalcaemia cause symptoms?

A

As with hypercalcaemia - no fixed level of blood calcium at which signs and/or symptoms develop, it varies from patient to patient, and may be influenced by comorbid conditions.

31
Q

What is the primary mechanism that causes symptoms of hypocalcaemia?

A

De-repression of activty - ie activation threshold is lowered and hyperactivity ensues.

32
Q

What are the main symptoms of hypocalcaemia?

A 
• Perioral tingling and parasthesia, 'pins and
needles‘ - earliest symptom.
• Tetany.
• Facial spasms.
• Hyperactive tendon reflexes.
• Laryngospasm.
• Cardiac arrhythmias.
33
Q

What is tetany?

A

A condition marked by intermittent muscular spasms, caused by malfunction of the parathyroid glands and a consequent deficiency of calcium.

34
Q

What are the causes hypocalcaemia?

A 
Hypoparathyroidism
– Postsurgical (most common)
– Autoimmune
– Pseudohypoparathyroidism (PTH resistance)
– Idiopathic

• Hypovitaminosis D
– Dietary deficiency
– Rickets, osteomalacia

• Organ dysfunction
– GI malabsorption, renal loss

• Endocrine response to non-hypoparathyroid hypocalcaemia
– Secondary hyperparathyroidism

35
Q

Name two common conditions caused by disorder of calcium metabolism.

A

Rickets and osteomalasia.

36
Q

Rickets primarily affects which age group?

A

Children

37
Q

What is rickets caused by?

A

A deficiency of Vitamin D in children – their bones has abnormal amounts of unmineralised osteoid.

38
Q

What are the signs and symptoms of rickets?

A

Bowing of long bones in the legs. Lack of bone rigidity which means bones are soft & easily fractured.

39
Q

What causes osteomalacia?

A

Deficiency of Vitamin D in adults:

•Increased unmineralised osteoid content results in a decline in bone strength.

40
Q

What are the signs and symptoms of osteomalacia?

A

• Long bone growth has completed in adults – bowing of weight-bearing bones does not occur, instead fractures develop.

CC 138 - Monoarthritis (3 decks)

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