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Clinical Pathology > Disorders of Calcium, phosphate and magnesium > Flashcards

Disorders of Calcium, phosphate and magnesium Flashcards

1
Q

Why is calcium physiologically important?

A

Muscle contraction
Neuronal signalling
Coagulation
Enzyme activity

Key mineral component of bone (hydroxyapatite)

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2
Q

What is the importance of phosphate?

A

ATP
Intracellular signalling
Cellular metabolic process
Backbone of DNA

INTRACELLULAR

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3
Q

What is the importance of magnesium?

A

Cofactor for ATP
Neuromuscular excitability
Enzyme fucntion
Ion channel regulation

INTRACELLULAR

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4
Q

What mechanisms are involved in homeostasis of ions?

A
  • Storage
  • Tissue redistribution
  • Intake (dietary)
  • Excretion
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5
Q

What are the key factors that control calcium levels?

A

PTH

Vit D

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6
Q

What is the only fraction of calcium that is physiologically active?

A

Ionised calcium

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7
Q

What other forms of calcium are there?

A

Bound calcium e.g. to albumin

Complexed - salts e.g. calcium phosphate, calcium citrate

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8
Q

What is the normal range for total calcium>

A

2.2-2.6 mol/L

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9
Q

What is the distribution for physiologically active Ca and inactive (i.e.bound/complexed)

A

50:50

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10
Q

How does alkalosis and acidosis change proportion of bound calcium?

A

Alkalosis - increased calcium-albumin, reduced ionised calcium

Acidosis - reduced calcium-albumin, increases ionised calcium

Because H+ ions compete with Ca++ for albumin binding sites

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11
Q

What can alkalosis cause?

A

Tetany - increased ionised calcium

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12
Q

What are the endogenous factors for vit D

A

Endogenous - skin colour, ageing

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13
Q

What are the exogenous factors for vit D

A

Ozone, sunscreen and clothing (cultural), season, time of day, supplements

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14
Q

What else does fit D fall with?

A

Age
BMI
body fat

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15
Q

Whats effect does PTH have on the gut?

A

Increased vit D release from kidney

Increased bit D increases calcium absorption from gut

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16
Q

What effect does PTH have on the kidney?

A

Reduced calcium clearance but increase phosphate excretion

17
Q

What effect does PTH have on bones?

A

Increased bone turnover with net reabsorption

18
Q

What its the plasma Ca?

A

Total Ca = ionised calcium + bound calcium + complexed calcium

19
Q

What is magnesium required for?

A

Release of PTH from zymogens

20
Q

What are the causes for hypocalcaemia?

A

Hypoproteinaemia - reduced album

Reduced vit D - dietry/malabsorption, hepatic/renal disease, end organ bit D resistance

Hypoparathyroidism - primary, secondary - Mg deficiency

Inadequate intake of calcium

21
Q

What does a low Ca but high PTH indicate?

A

Vit D deficiency

22
Q

What does a low Cal, high phosphate and low PTH indicate?

A

Hypothyroidism (primary or secondary to magnesium def)

23
Q

What are the simple clinical features of hypercalcaemia?

A

Stones bones (pain) moans (ab pain) and groans (load mood/depression)

24
Q

What are the causes of hypercalcaemia?

A 
Hyperparathyroidism
Malignancy e.g. primary tumour of PT
Bone disease and immobilisation
Excessive vit D 
Drugs e.g. lithium
25
Q

If you have high Ca, high PTH and low phosphate, whats the cause?

A

Hyperparathyroidism

26
Q

If you have high calcium and low PTH, whats the cause?

A

Bone malignancy

27
Q

What are the main causes of phosphate deficiency?

A

-Hyperparathyroidism
-Excess losses - renal tubule damage, GI, diabetes (diuresis)
- Insufficient intake - malnutrition
ECF/ICF redistribution e.g. refeeding

28
Q

What are the symptoms of phosphate deficiency?

A
  • Haemolysis, thrombocytopenia, poor granulocyte function
  • Muscle weakness, resp muscle failure, rhabdomyolysis
  • confusion/irritability
29
Q

What is hypomagnesaemia associated with?

A

Hypokalaemia
Hyponatraemia
Hypophosataemia
Hypocalcaemia

LOOK AT THESE!!!

30
Q

What is the major causes of hypomagnesaemia?

A

Renal - acute tubular necrosis
Hypercalaemic states
Drugs e.g. antibiotics, diuretics
GI - malnutrition, diarrhoea, malabsorption

31
Q

What are the effects of magnesium depletion?

A

Cofactor of ATP - so anything requiring ATP in effected!

Impaired PTH release - required for PTH release from zymogens

Clinical Pathology (50 decks)

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