Brainscape's Knowledge GenomeTM

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


See full index

Nephrology and Hypertension Board Review > Chapter 3 Calcium, Phosphorus, Magnesium, and Kidney Stones > Flashcards

Chapter 3 Calcium, Phosphorus, Magnesium, and Kidney Stones Flashcards

1
Q

What percentage of total body calcium is stored in bones and teeth?

A

99% of total body calcium is stored in bones and teeth.

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

Outside of bones and teeth, where else is calcium stored in the body?

A

1% of total body calcium is found in the intracellular fluid compartment.

0.1% of total body calcium is found in the extracellular fluid compartment.

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

How is calcium in plasma stored?

A

Calcium in plasma comes as:

  • Ionised calcium (40 - 50%)
  • Protein bound, mainly to albumin (40 - 50%)
  • Complexed (to phosphate, citrate and bicarbonate) (10%).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What changes the distribution of plasma calcium?

A

pH and levels of albumin change the distribution of plasma calcium.

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

How does acidaemia change the distribution of plasma calcium?

A

Acidaemia increases the percentage of ionized calcium at the expense of calcium bound to proteins.

  • Increased hydrogen ions in acidaemia bind to plasma proteins, displacing calcium from plasma proteins and increasing the relative concentration of ionised calcium.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does alkalaemia change the distribution of plasma calcium?

A

Alkalemia decreases the percentage of ionized calcium.

  • Decreased hydrogen ions in alkalaemia results in some dissociating from plasma proteins, in exchange for calcium, thereby decreasing the plasma concentration of ionized calcium.

]. Hypoalbuminemia increases the ionized [Ca ++ ], whereas hyperalbuminemia decreases ionized plasma [Ca ++

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

Are individuals with alkalaemia or acidaemia more susceptible to tetany with hypocalcaemia?

A

Alkalaemia

Individuals with alkalemia are susceptible to tetany (tonic muscular spasms), whereas individuals with acidemia are less susceptible to tetany with hypocalcaemia.

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

How does the proportion of ionised calcium change with differing levels of albumin?

A

Ionised calcium increases with hypoalbuminaemia.

Ionised calcium decreases with hyperalbuminaemia.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

In brief, what are the four physiological functions of calcium?

A
  1. Skeletal composition
  2. Neuromuscular excitation
  3. Skeletal muscle contraction
  4. Cardiac muscle contraction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is normal dietary calcium intake per day?

A

Normal dietary calcium intake is 1g per day.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What percentage of dietary calcium is absorbed by the gastrointestinal tract?

A

20% of dietary calcium is absorbed by the gastrointestinal tract.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does calcitriol do?

A

Calcitriol (1,25 vitamin D) binds to its VDR receptor and:

  • Increases TRPV6 expression
  • Increases calbindin D9K
  • Increases Calcium ATPase

These all increase calcium absorption from the gut.

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

In brief, what is TRPV6?

A

TRPV6 (transient receptor potential) is a calcium channel that facilitates apical uptake of calcium by enterocytes.

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

What increases intestinal calcium absorption?

A

Increased intestinal calcium absorption occurs in:

  • Acromegaly
  • Excess vitamin D ingestion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What decreases intestinal calcium absorption?

A

Decreased intestinal calcium absorption occurs in:

  • High vegetable fibre diet
  • Low calcium/phosphate ratio diets
  • High fat diet
  • Older patients
  • Oestrogen deficiency
  • Corticosteroid use
  • Diabetes
  • Kidney disease
  • Gastrectomy
  • Bowel malabsorption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What percentage of calcium is ultra filterable?

A

55% of calcium is ultrafilterable (diffusible) - ionised calcium and complexed calcium.

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

What factors influence the load of ultrafilterable calcium?

A

The factors that influence the ultrafilterable calcium load are:

  • Glomerular filtration rate
  • Glomerular surface
  • Ultrafiltration coefficient Kf
  • Ultrafilterable calcium load.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does PTH do to the ultrafiltration coefficient Kf?

A

PTH reduced the ultrafiltration coefficient Kf.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What hormones increase distal calcium reabsorption?

A

PTH and calcitriol increase distal calcium reabsorption.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What drugs increase calcium reabsorption in the distal tubules?

A

Amiloride and thiazides increase calcium reabsorption in the distal tubules.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the daily urinary excretion of calcium?

A

The daily urinary excretion of calcium is <0.3g/d, which is minimal given the amount that is filtered and this is due to its effective reabsorption along the entire nephron.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the most biologically active form of vitamin D?

A

1,25 vitamin D is the most biologically active form of vitamin D.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What does 1,25 vitamin D do?

A

1,25 vitamin D:

  • Increases GI absorption of calcium and phosphate
  • Stimulates FGF-23 and 24-hydroxylase
  • Provides negative feedback on PTH.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the primary function of PTH?

A

The primary function of PTH is to increase ionised calcium levels in response to hypocalcaemia.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

In brief, what are the function of PTH?

A

PTH:

  • Induces phosphaturia
  • Increases 1,25 vitamin D.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How is FGF-23 produced?

A

FGF-23 is a peptide produced by osteocytes and osteoblasts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

In brief, what are the main actions of FGF-23?

A
  1. Phosphaturia
  2. Inhibition of PTH
  3. Reduces 1,25 vitamin D activity
28
Q

How does FGF-23 cause phosphaturia?

A

FGF-23 suppresses two genes that encode sodium-phosphate transporters in the proximal tubules.

FGF-23 suppresses NPT2a and NPT2b.

29
Q

What causes upregulation of FGF-23?

A

FGF-23 is upregulated by phosphate, although not necessarily hyperphosphataemia, and 1,25 vitamin D.

30
Q

In brief, what are the causes of hypercalcaemia?

A
  1. Excess calcium ingestion
  2. Excessive vitamin D ingestion
  3. Bone metastatic disease
  4. Osteoclastic activating factors from malignancy
  5. Immobilisation
  6. Primary hyperparathyroidism
  7. Granulomatous disease
  8. Medications
  9. Familial hypocalciuric hypercalcaemia
  10. Jansen disease
  11. Paget disease
  12. Loss of function of vitamin D-24-hydroxylase
31
Q

What are the causes of primary hyperparathyroidism?

A
  1. Parathyroid adenoma (80%)
  2. Diffuse parathyroid hyperplasia (15%)
  3. Carcinoma (5%).
32
Q

What is latent primary hyperparathyroidism?

A

Latent primary hyperparathyroidism may present as:

  • Normocalcaemic hyperparathyroidism
  • Hypercalcaemic normoparathyroid.

Latent primary hyperparathyroidism has a high likelihood of developing overt hyperparathyroidism.

33
Q

What granulomatous diseases can cause hypercalcaemia?

A

Granulomatous diseases that can cause hypercalcaemia include:

  1. Sarcoidosis
  2. Tuberculosis
  3. Beryllosis
34
Q

How do granulomatous diseases cause hypercalcaemia?

A

Increased 1alpha-hydroxylase activity within macrophages in granulomas results in high 1,25 vitamin D (and low PTH) levels.

35
Q

What medications can lead to hypercalcaemia?

A

Medications that can cause hypercalcaemia include:

  1. Lithium
  2. Thiazide diuretics
  3. Antacids
  4. Vitamin A.
36
Q

What is the cause of familial hypercalcaemic hypocalciuria?

A

Familial hypercalcaemic hypocalciuria is a rare autosomal dominant condition characterised by inactivating mutations of CaSR.

As CaSR is inactivated it does not sense presence of hypercalcaemia to induce facilitated calciuria.

Familial hypercalcaemic hypocalciuria is characterised by moderate chronic hypercalcaemia, normo- to hypophosphataemia, and hypocalciuria.

37
Q

What is the PTH level in familial hypercalcaemic hypocalciuria?

A

PTH is normal to elevated in familial hypercalcaemic hypocalciuria.

38
Q

How can primary hyperparathyroidism and familial hypercalcaemic hypocalciuria be differentiated?

A

Primary hyperparathyroidism and familial hypercalcaemic hypocalciuria can be differentiated by the fractional excretion of calcium.

The fractional excretion of calcium is LOW in familial hypercalcaemic hypocalciuria.
The fractional excretion of calcium is HIGH in primary hyperparathyroidism.

39
Q

What is Jansen disease?

A

Jansen disease is caused by an activating mutation of the PTH/PTHrP receptor gene.

Jansen disease is manifested by short-limbed dwarfism, severe hypercalcaemia, hypophosphataemia and metaphysical chondrodysplasia.

40
Q

What is the consequence of a loss of function mutation of vitamin D-24 hydroxylase?

A

A loss of function mutation of vitamin D-24 hydroxylase leads to high levels of 1,25 vitamin D and hypercalcaemia.

Clinically there is hypercalcaemia and nephrocalcinosis/nephrolithiasis.

41
Q

What is the treatment of a loss of function mutation of vitamin D-24 hydroxylase?

A

Ketoconazole is an inhibitor of vitamin D 1 alpha hydroxylase and corrects hypercalcaemia in patients with a loss of function mutation of vitamin D-24 hydroxylase.

42
Q

What drugs can induce a hyperparathyroidism picture?

A

The tyrosine kinase inhibitors (sunitinib and imatinib) can cause hypocalciuria and normal to high serum calcium, hypophosphataemia, and elevated 1,25 vitamin D levels.

43
Q

How do loop diuretics affect calcium?

A

Loop diuretics enhance paracellular calcium excretion from the thick ascending limb of the loop of Henle.

44
Q

What are the clinical manifestations of hypercalcaemia?

A

Hypercalcaemia is manifested by:
Neuro: Fatigue, poor concentration, headaches, depression, anxiety

Ocular: conjunctivitis, band keratopathy

Cardiac: shortened QT, arrhythmias

Gastrointestinal: constipation, nausea, vomiting, peptic ulcer disease, pancreatitis

Kidney: polyuria, nephrogenic diabetes insipidus, nephrocalcinosis, nephrolithiasis.

45
Q

What is the first step of management in hypercalcaemia?

A

The first step of management of hypercalcaemia is volume repletion with normal saline.

46
Q

What agents are available to manage hypercalcaemia?

A
  1. Loop diuretics
  2. Bisphosphonates
  3. Corticosteroids
  4. Ketoconazole
  5. Calcimimetics
47
Q

What other drugs could be used in management of hypercalcaemia?

A
  1. Mithramycin
  2. Propanolol
  3. Oestrogens
48
Q

What is denosumab?

A

Denosumab is a human monoclonal antibody that binds to and inhibits RANKL.

RANKL increases bone resorption.

49
Q

What is the caution using denosumab?

A

Denosumab can cause severe hypocalcaemia, particularly in patients with advanced kidney disease.

50
Q

What are the indications for parathyroidectomy for primary hyperparathyroidism?

A
  1. Serum calcium > 1.0mg/dL (> 0.25 mmol/L) above upper limit of normal
  2. Hypercalciuria > 400mg/d or kidney stones
  3. Creatinine clearance < 30% of normal
  4. Marked bone density reduction with T score
51
Q

What imaging studies are recommended prior to surgery for hyperparathyroidism?

A

99mTc sestimibi scintigraphy +/- single photon emission computed tomography (SPECT) and ultrasound are recommended prior to surgical management of hyperparathyroidism.

These imaging studies allow localisation to facilitate minimally invasive surgery for adenomas instead of exploratory surgery.

52
Q

What is hungry bone syndrome?

A

Hungry bone syndrome is characterised by profound and prolonged hypocalcaemia following parathyroidectomy for hyperparathyroidism.

Profound = serum calcium < 6mg/dL (< 1.5 mmol/L)
Prolonged = > 4 days postoperatively
53
Q

What are risk factors for hungry bone syndrome?

A

Risk factors for hungry bone syndrome include:

  1. Osteitis fibrosa cystica
  2. Brown tumours
  3. Severe hyperparathyroidism
54
Q

What are the cause s of pseudohypocalcaemia?

A

Pseudohypocalcaemia is caused by:

  1. Alkalosis: clinically significant reduction in ionised calcium with normal serum calcium levels
  2. Hypoalbuminaemia: low total serum calcium with normal ionised calcium levels.
55
Q

How can hypocalcaemia be classified?

A

Hypocalcaemia can be classified according to phosphate level.

56
Q

What are the causes of hypocalcaemia with low to normal phosphate?

A

Hypocalcaemia with low to normal phosphate is caused by:

  1. Hungry bone syndrome
  2. Magnesium deficiency
  3. Malnutrition
  4. Acute pancreatitis
  5. Vitamin D deficiency
  6. Vitamin D resistance.
57
Q

What are the causes of hypocalcaemia with hyperphosphataemia?

A

Hypocalcaemia with hyperphosphataemia is caused by:

  1. Kidney failure
  2. Rhabdomyolysis
  3. Pseudohypoparathyroidism
  4. Hypoparathyroidism
  5. Autosomal dominant hypoparathyroidism
58
Q

What are the causes of vitamin D deficiency?

A

Vitamin D deficiency can be caused by:

  1. Vitamin D 25 deficiency
  2. Vitamin D 1,25 deficiency
  3. Liver disease
  4. Anticonvulsants
59
Q

What are the causes of hypoparathyroidism?

A

Hypoparathyroidism can be caused by:

  1. Neck irradiation
  2. Amyloid infiltration of parathyroid glands
  3. Idiopathic
  4. Post-operative.
60
Q

What is your approach to hypocalcaemia in rhabdomyolysis?

A

Hypocalcaemia in rhabdomyolysis should not be treated, except with evidence of ECG or neurological changes.

  1. Hypocalcaemia is transient related to calcium sequestration in injured tissue
  2. PTH is stimulated in initial hypocalcaemic phase and can contribute to hypercalcaemia if additional treatment
  3. Calcium infusion in presence of hyperphosphataemia can lead to vascular and soft tissue calcifications.
61
Q

What is autosomal dominant hypoparathyroidism?

A

Autosomal dominant hypoparathyroidism is caused by activating mutations of CaSR.

Autosomal dominant hypoparathyroidism results in hypercalciuria and hypocalcaemia.

62
Q

What is the opposite to familial hypocalciuric hypercalcaemia?

A

Autosomal dominant hypoparathyroidism is the opposite to familial hypocalciuric hypercalcaemia.

63
Q

What two important rules must be remembered in management of hypocalcaemia?

A

In management of hypocalcaemia:

  1. With concurrent acidaemia, hypocalcaemia must be corrected FIRST.
  2. Calcium cannot be given in same intravenous line as sodium bicarbonate due to calcium precipitation as calcium carbonate.
64
Q

What is the concern regarding correction of acidaemia with hypocalcaemia?

A

Alkalinization may acutely reduce circulating levels of ionised calcium.

65
Q

Why is calcium gluconate preferred to calcium chloride?

A

Calcium gluconate is preferred to calcium chloride because it is less irritating to peripheral veins.

Calcium chloride can be used where there is central access.

66
Q

In brief, how can severe hypocalcaemia be managed?

A

Severe hypocalcaemia can be managed as follows:

  1. IV 10ml of 10% calcium gluconate diluted in 50mL given over 5 - 10 minutes.

If no improvement

  1. IV 8 - 10 ampoules of calcium gluconate in 1 L of normal saline or 5% dextrose to run over 24 hours.

Nephrology and Hypertension Board Review (4 decks)

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