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3006 Clin. Biochem > Calcium disorders > Flashcards

Calcium disorders Flashcards

1
Q

ROle of calcium

A
  • bone formation
  • muscle contraction
  • Signalling
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2
Q

3 sources for calcium (where body gets ca)

A
  • Absorption via S. Int w/ Vit D
  • Resorption via bone
  • Reabsorbtion via kidneys
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3
Q

a inc/dec in [2x ions] excites nerve/muscle cells

A

inc Ca = excite nerves
low K = excite nerves = weakness
(Hi K = cardiac arrest)

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4
Q

total plasma calcium =

A

ionised Ca + Ca bound/complex w/ Alb

*equ. need to be adjusted in hypocalcemia

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5
Q

ROle of phosphate

A
  • bone formation
  • component for dNTP
  • energy cycles
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6
Q

What is Rhabdomyolysis

A

major injury & muscle damage = inc PO4 bind to Ca2+ => hypocalcemia

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7
Q

hormones involved in regulating Ca & role

A
  • PTH: increase Ca & dec PO4 in blood
  • Vit D: inc Ca & PO4 in blood
  • Calcitonin: reduce Ca in blood
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8
Q

which plasma Ca is biologically active?

A

Ca2+ (ionised Ca)

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9
Q

Most of body’s phosphate, calcium and magnesium are in

A

skeletal

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10
Q

How can blood pH affect ionised Ca?

A
  • H+ competes w/ Ca2+ for binding w/ Alb (-ve) => Free Ca2+
  • acidosis = Hi H+ = More Ca2+ (ionised form)
  • Alkalosis = Lo H+ = Less Ca2+
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11
Q

relationship of PO4 & Ca

A

inverse proprtional

inc. PO4 = dec Ca2+

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12
Q

Normal calcium metabolism depends on (5)

A
  • Parathyroid (PTH) function
  • Renal function (creatinine)
  • Intestinal Function
  • Adequate supply of vitamin D - made in kidneys
  • Adequate supply of calcium
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13
Q

Which of the following hormones is often associated with malignancy?

A

PTHrP

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14
Q

how is PTH release stimulated

A
  • hypocalcemia
  • hyperphosphatemia
  • hypermagnesiemia
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15
Q

Why children are having high ALP?

A

Because they have high osteoblast

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16
Q

how active vit D is formed

A
  1. In skin, UV irradiation converts 7-dehydroxycholesterol => cholecalciferol (Vit. D)
  2. => 25-dihydroxycholecalciferol in liver
  3. => active Vit D = 1,25 (OH)2 vit D3 (calcitriol) in the kidneys by 1 alpha hydroxylase
17
Q

Rickets vs Osteomalacia

A
  • Poor bone mineralization due to VitD3 deficiency or calcium
    => Rickets: soft bones in CHILDREN OR
    OR => Osteomalacia: soft bones in ADULTS
18
Q

causes of Vit Ddeficiency

A
  • Hi altitudes = low exposure to sunlight
  • Malabsorption of food in GIT
  • Renal disease
  • hypothyroidism
19
Q

effects of hypercalcemia from excess vit D

A
  • Calcium deposition in soft tissues
  • Renal damage
  • Cardiac damage
20
Q

Action of PTH & Vit D in stimulating osteoclast activity

A
  1. PTH stimulates 1-a-hydroxylase to convert inactive Vit D into (1,25(OH)2-VitD3)
  2. => osteoblast ligand (RANKL) expressed
  3. osteoclast activity inc = bone resorption = inc Ca in blood
21
Q

role of Calcitonin

A
  • Lowers plasma phosphate
  • Lowers plasma calcium
  • Inhibits actions of PTH
  • Inhibits actions of calcitriol
22
Q

Causes of hypOcalcaemia

A
  • Hepatobiliary diseases
  • Magnesuim deficiency
  • Vit D deficiency
  • Hypoparathyroidism
23
Q

Name the condition: lack of renal response to PTH due to kidney resistance to PTH.

A

Pseudohypoparathyroidism

24
Q

Causes of hypERcalcaemia

A
  • PTHrp
  • Hyperparathyroidism
  • Multiple myeloma
  • High albumin
  • Vit D intoxication
25
Q

Where renal failure is the most common cause of _calcemia

A

hypocalcemia

26
Q

Bone is impregnated with Ca10(PO4)6(OH)2, which is named ——–.

A

hydroxyappetite

27
Q

what is this 1,25(OH)2VitD3 (1,25-dihydroxycholecalcitriol)

A

active form of Vit D aka calcitriol

28
Q

Enzyme responsible for activating Vit D

A

1 alpha hydroxylase

29
Q

possible cause for hypocalcemia & why?

A

Chronic kidney disease

30
Q

role/relevance of magnesium in calcium homeostasis

A
  • influences PTH release

- (Low Ca + Hi PO4) => inc Mg => PTH release => activates Vit D => inc mechanisms to inc Ca in blood

3006 Clin. Biochem (13 decks)

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