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Endocrine System > Sodium and Calcium Homeostasis > Flashcards

Sodium and Calcium Homeostasis Flashcards

1
Q

What stimuli increase to production of ADH?

A

Decreased plasma volume sensed by baroreceptors

Increased plasma osmolality sensed by osmoreceptors in the hypothalamus

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2
Q

Osmolality is mainly determined by the amount of extracellular water. What are the main mechanisms which regulate water status?

A

ADH

Thirst

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3
Q

How is hyponatraemia defined?

A

serum sodium <135mmol/l

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4
Q

Hyponatraemia is the most common disorder of electrolyte balance in clinical practice. T/F?

A

True

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5
Q

How are hyponatraemia and ADH related?

A

Hyponatraemia is almost always due to a disorder of water balance as a result of an inability to suppress ADH release resulting in inappropriate retention of water

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6
Q

Extrarenal losses of water and sodium can result in hyponatraemia and hypovolaemia. What might result in extra renal losses?

A 
Vomiting
Diarrhoea
Burns
Pancreatitis
Traumatised muscle
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7
Q

What might cause hyponatraemia when there is normal sodium but excess water in the body?

A 
Hypothyroidism
Glucocorticoid deficiency
pain
psychiatric disorders
drugs
syndrome of inappropriate ADH secretion
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8
Q

What can cause syndrome of inappropriate ADH?

A 
Cancer (lung, leukaemia, lymphoma)
chest disease (pneumonia)
CNS disorders (infections, injury or drugs)
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9
Q

A sudden decrease in sodium concentration can cause cerebral oedema. How does this happen?

A

The decrease in sodium concentration means that water moves out of the blood and into the cells to increase the plasma osmolality and this causes swelling of the cells

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10
Q

What change is serum sodium concentration can result is osmotic demyelination syndrome?

A

Increase in sodium

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11
Q

Hyponatraemia is often asymptomatic. T/F?

A

True

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12
Q

What are the symptoms of hyponatraemia?

A 
Mild confusion
Gait instability
Marked confusion
Drowsiness
Seizures
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13
Q

Severe and acute hyponatraemia can present with unconsciousness or seizures. How is this treated?

A

Infusion of hypertonic (4%) saline

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14
Q

How is less severe or chronic hyponatraemia managed?

A

Fluid restriction

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15
Q

What is the controversial second line treatment of mild or chronic hyponatraemia?

A

AVPR2 antagonists

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16
Q

What are the most common causes of hypernatraemia?

A

Loss of water through sweat losses (burns, sepsis), Gi losses, diabetes insidious and osmotic diuresis
inability to access water

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17
Q

How can the water deficit in patients with hypernatraemia be calculated?

A

water deficit - current total body water (50-60% of lean body weight) x ((serum sodium/140)-1)

18
Q

A fluid regime to treat a water deficit causing hypernatraemia should be done gradually. You should aim for a decrease of 10mmol/l of sodium every how many hours?

A

24 hours

19
Q

What fluid is used when treating a water deficit in a hypernatraemic patient?

A

IV 5% dextrose

20
Q

What percentage of calcium is reabsorbed in the kidney?

A

97-99%

21
Q

What affects does vitamin D have on serum calcium levels and how does it achieve this?

A

Increases Gi absorption of calcium, increases bone resorption and increases renal reabsorption which leads to an overall increase in serum calcium

22
Q

Which hormone is the main regulator of calcium homeostasis?

A

PTH

23
Q

Bone acts as a reservoir for which mineral?

A

Calcium

24
Q

What percentage of serum calcium is free or ionised?

A

45%

25
Q

To which protein is calcium bound in the blood?

A

Albumin

26
Q

What are the clinical features of hypercalcaemia?

A 
Polyuria
Polydipsia
Nephrolithiasis
Nephrocalcinosis
Distal renal tubular acidosis
Nephrogenic diabetes insipidus
anorexia
nausea
vomiting
pancreatitis
peptic ulcer disease
muscle weakness
bone pain
osteopenia
oestoporosis
decreased concentration
confusion 
fatigue
27
Q

What affect does hypercalcaemia have on heart rate?

A

Slows heart rate

28
Q

What can cause hypercalcaemia?

A 
Primary hyperparathyroidism (usually single parathyroid adenoma)
Malignancy where the tumour is secreting PTH-related peptide
29
Q

How can PTH measurement help to determine to cause of hypercalcaemia?

A

PTH is decreased then malignancy most likely

PTH normal or increased the primary hyperparathyroidism most likely

30
Q

What is classified as mild hypercalcaemia?

A

<3mmol/l

31
Q

What is classified as moderate hypercalcaemia?

A

3-3.5mmol/l

32
Q

What is classified as severe hypercalcaemia?

A

> 3.5mmol/l

33
Q

Patients with hyperclacaemia are often hypovolaemia and this impairs renal clearance of calcium. How is this hypovolaemia treated?

A

0.9% IV saline

34
Q

What drugs are most commonly used when treating hypercalaemia as a result of malignancy?

A

Bisphosphonates

35
Q

Calcitonin can be given in the treatment of hypercalcaemia. How does this work?

A

Increases renal calcium excretion and decreases bone resorption

36
Q

Bisphosphonates can be given in the treatment of hypercalcaemia. How does this work?

A

Inhibit osteoclasts to inhibit bone resorption

37
Q

Glucocorticoids can be given in the treatment of hypercalcaemia. How does this work?

A

Vitamin D production

38
Q

In some cases parathyroidectomy may be used to treat hypercalcaemia. T/F?

A

True

39
Q

What are the clinical features of hypocalcaemia?

A 
Tetany
Peri-orbital numbness
Muscle cramps
Tingling of the hands and feet
Caropedal spasm
Laryngospasm
Seizures
40
Q

What are the possible causes of hypocalcaemia?

A

Low PTH (following surgery or autoimmune)
High PTH due to vitamin D deficiency, chronic renal failure or loss of calcium
Drug use
Hypomagnesaemia (leading to PTH resistance)

41
Q

How is chronic hypocalcaemia managed?

A

Vitamin D supplementation and calcium salts

42
Q

How is acute hypocalcaemia treted?

A

IV calcium replacement possibly alongside magnesium replacement

Endocrine System (12 decks)

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