Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Clinical Pathology > Disorders of calcium, phosphate and magnesium. > Flashcards

Disorders of calcium, phosphate and magnesium. Flashcards

1
Q

What is the physiological importance of calcium?

A
  • Muscle contraction
  • Neuronal excitation
  • Enzyme activity (Na/K ATPase, hexokinase etc.)
  • Blood clotting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the structural importance of calcium?

A

Key component of hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ - the predominant mineral in bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the physiological importance of phosphate (PO4-)

A
  • The P in ATP – our fuel!
  • Intracellular signalling
  • Cellular metabolic processes e.g. glycolysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the structural importance of phosphate?

A
  • Backbone of DNA
  • Component of hydroxyapatite Ca₁₀(PO₄)₆(OH)₂
  • Membrane phospholipids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the physiological importance of magnesium?

A
  • Cofactor for ATP
  • Neuromuscular excitability
  • Enzymatic function
  • Regulates ion channels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the normal range for calcium?

A

2.20 -2.60 mmol/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the two key controlling factors for calcium?

A
  • PTH

- Vitamin D and metabolites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What processes is calcium related to/involved in?

A
  • GI uptake
  • Renal Clearance
  • Bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is plasma calcium?

A

Total Ca = Ionised Ca + Bound Ca + Complexed Ca

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is ionised calcium?

A

Physiologically active fraction

  • Calcium sensing receptor
  • Cellular Effects
  • Regulation of PTH
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is bound calcium?

A

Bound Calcium

  • Physiologically inactive
  • Albumin main binding protein (~50%)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is complexed calcium?

A

Salts – calcium phosphate & calcium citrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What can calcium values be corrected for?

A

Changes in albumin. Better diagnostic performance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What effect does acidosis have on Ca-albumin?

A

Reduces Ca-albumin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What effect does alkalosis have on Ca-albumin?

A

Increases Ca-albumin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can alkalosis precipitate?

A

Tetany

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the endogenous factors related to Vit D absorption?

A
  • Skin colour

- Aging

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the exogenous factors related to Vit D absorption?

A
  • Ozone
  • Sunscreens & clothing
  • Latitude and season
  • Time of day
  • Diet & supplements
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What factors cause vitamin D to fail?

A
  • Age
  • Body fat
  • BMI
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the role of parathyroid hormone (PTH)?

A

Acts on bone, GI and kidney to increase levels of ionic calcium. Increased ionic Ca acts upon the parathyroid glands to stop the release of PTH.

21
Q

What is the effect of PTH on the kidney?

A

Decreases Ca clearance but increases phosphate excretion.

22
Q

What is the effect of PTH on bone?

A

Increases Ca turnover with net resorption.

23
Q

What is the effect of PTH on the gut?

A

Stimulates the kidney to release vit D.

Vit D increases Ca absorption from the gut.

24
Q

What are the causes of hypocalcaemia?

A
  • Hypoproteinaemia
  • Vit D deficiency
  • Hypoparathyroidism
  • Inadequate intake of Ca
  • Pseudohypoparathyroidism
  • Artefactual causes
25
Q

What are the causes of Vit D deficiency?

A
  • Dietary / Malabsorption
  • Hepatic disease
  • Renal Disease
  • End organ Vitamin D resistance
26
Q

What are the causes of hypoparathyroidism?

A
  • Primary

- Secondary to Mg depletion

27
Q

What is the cause of pseudohyoparathyroidism?

A

End organ PTH resistance.

28
Q

What are the artefactual causes of hypocalcaemia?

A
  • EDTA contamination

- Venestasis will cause low adjusted calcium (total calcium is unaffected)

29
Q

How can you tell the difference between hypoparathyroidism and Vit D deficiency?

A

Vit D deficiency - High PTH, low Ca

Hypoparathyroidism - rock bottom PTH, low Ca

30
Q

What are the possible causes of hypercalcaemia?

A

Hyperparathyroidism

Malignancy

  • Lytic lesions
  • Humoral eg PTHrp

Drugs

Vitamin D excess

  • 1a cholecalciferol
  • Sarcoidosis

Bone disease + immobilisation

31
Q

What is the most common cause of ludicrously serum high potassium.

A

EDTA comtamination

32
Q

What are the differential diagnoses of hypercalcaemia?

A
  • Consider Adjusted Ca: look at the albumin
  • Check drug history
  • Exclude excess vitamin D intake
  • Check for renal failure
  • Simultaneous measurement of Ca & PTH
  • Consider rarer causes & more complex investigations
33
Q

How can you tell the difference between hyperparathyroidism and bone metastases?

A

Hyperparathyroidism - high PTH, high calcium

Metastases - low PTH, high calcium

34
Q

What are the causes of phosphate deficiency?

A

Hyperparathyroidism

Excess losses

  • renal tubular damage
  • Gastro intestinal
  • diabetes (diuresis)

Poor intake

  • malnutrition
  • inadequate IVN

ECF / ICF redistribution - like potassium

35
Q

What are the signs/symptoms of phosphate deficiency?

A
  • Haemolysis, thrombocytopenia and poor granulocyte function
  • Severe muscle weakness, respiratory muscle failure and rhabdomyolysis
  • Confusion, irritability and coma may be due to a metabolic encephalopathy due to phosphate deficiency
  • Renal dysfunction
36
Q

What is hypomagnesaemia associated with?

A

Hypokalaemia Hyponatraemia Hypophosataemia

Hypocalcaemia

37
Q

What are the renal causes of magnesium depletion?

A
  • Diuretic phase of Acute
  • Tubular Necrosis
  • Hypercalcaemic states
  • Drugs
    • Antibiotics - gentamicin/carbenicillin
    • Chemotherapy - cisplatin
    • Diuretics
    • FK506
38
Q

What are the GI causes of magnesium depletion?

A
  • Malnutrition
  • Intravenous nutrition
  • Diarrhoea
  • Malabsorption
39
Q

What are the cellular effects of magnesium depletion?

A
  • Reduced mitochondrial respiration & impaired phosphorylation
  • Defective Na-K ATPase activity
  • Impaired DNA synthesis
40
Q

What are the biochemical effects of magnesium depletion?

A
  • Hypocalcaemia
  • Hypophosphataemia
  • Hypokalaemia
41
Q

What are the endocrine effects of magnesium depletion?

A
  • Impaired PTH release

- PTH resistance in bone

42
Q

What are the cardiovascular effects of magnesium depletion?

A
  • Cardiac irritability

- Reduced contractility

43
Q

What are the CNS effects of magnesium depletion?

A
  • Hyper-reflexia
  • Tetany
  • Ataxia / Vertigo
  • Psychosis / Depression
44
Q

What are the muscle effects of magnesium depletion.

A
  • Weakness
  • Muscle fibrillation
  • Myopathic EMG
45
Q

What is the relevance of serum magnesium?

A
  • Poor correlation with Mg status

- Of value acutely

46
Q

What is the relevance of erythrocyte Mg?

A
  • Poor correlation with Mg status

- Affected by high reticulocyte count

47
Q

What is the relevance of leukocyte Mg?

A
  • Good correlation

- Good predictive value

48
Q

What is the relevance of muscle Mg?

A
  • 20% body mass
  • important physiologically
  • requires biopsy
49
Q

When should magnesium screening be considered?

A

With combined hypokalaemia and hypocalcaemia

Clinical Pathology (65 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions