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D&E Pathology > Clinical Calcium Homeostasis > Flashcards

Clinical Calcium Homeostasis Flashcards

1
Q

What are the dietary sources of calcium?

A

Milk/dairy
Broccoli, cabbage
Bony fish
Nuts

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2
Q

What is the function of calcium?

A

Neurotransmitter release
Bone formation
Cell division/growth
Muscle contraction

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3
Q

Where is calcium stored and in what proportions?

A

BONE - 99%
Cells - 1%
Extracellular fluid - 0.1%

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4
Q

What proportion of plasma calcium is bound?

A

45% bound to protein
10% Bound to other things
45% ionised - free

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5
Q

What is normal calcium?

A

2.2-2.6mmol/L

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6
Q

What is the effect of increased albumin on calcium?

A

Decreased free calcium

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7
Q

How do we adjust calcium for albumin levels?

A

0.1mmol calcium change for each 5g reduction in albumin from 40g

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8
Q

What is the effect of decreased albumin on calcium?

A

Increased free calcium

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9
Q

What is the effect of acidosis on calcium?

A

Increased ionised calcium - predisposes to hypercalcemia

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10
Q

What are the dietary sources of vitamin D?

A

Oily fish
Eggs
Fortified spreads/cereals

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11
Q

What do chief cells respond to in the parathyroid?

A

Changes in calcium concentrations

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12
Q

Changes in calcium ECF are sensed by what?

A

Calcium-sensing receptor

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13
Q

Increased calcium has what effect on the parathyroid?

A

Decreased PTH secretion

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14
Q

Decreased calcium has what effect on the parathyroid?

A

Increased PTH secretion

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15
Q

Lengthy exposure to increased PTH can lead to what?

A

Osteoporosis

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16
Q

What is the role of PTH?

A

Increased Ca2+ resorption from gut, renal tubules, bones

Mediates conversion of vitamin D to Calcitriol

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17
Q

What is vitamin D converted into in the liver?

A

25(OH) Vitamin D (inactive)

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18
Q

Which enzyme in the liver converts vitamin D, and what does it convert it to?

A

Vitamin D 25-hydroxylase

25(OH) Vitamin D (inactive)

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19
Q

Which enzyme in the kidney converts inactive vitamin D, and what does it convert it to?

A

25(OH) Vitamin D1a-hydroxylase

1,25(OH)2 Vitamin D (Active)

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20
Q

Which patients need activated vitamin D?

A

Low vitamin D in renal failure

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21
Q

What are the clinical features of acute hypocalcaemia?

A 
TETANY
PAPILLOEDEMA
Trousseaus sign
Chovstek's sign
Seizures
Parasethesia/twitching
Carpopedal spasm
Prolonged QT
Hypotension
Arrhythmia
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22
Q

When do symptoms of hypocalcaemia tend to develop?

A

Below 1.9mmol/L

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23
Q

What are the clinical features of chronic hypocalcaemia?

A 
Ectopic calcification
Extrapyramidal signs
Parkinsonism
Dementia
Subcapsular cataracts
Abnormal dentition
Dry skin
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24
Q

What is Trosseau’s sign?

A

Sign of hypocalcaemia

Clawed wrist flexion when BP cuff inflated

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25
Q

What is Chovstek’s sign?

A

Sign of hypocalcaemia
Relax face, trap facial nerve
Corner of lip twitches towards finger

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26
Q

What is the most likely cause of hypocalcaemia in a recent thyroid surgery patient?

A

PTH gland damage/selective parathyroidectomy

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27
Q

What are the causes of hypocalcaemia with low PTH?

A 
(Hypoparathyroidism)
Post-surgery (thyroidectomy, parathyroidectomy)
Autoimmune
Infiltration
Radiation damage
Hungry bone syndrome
HIV
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28
Q

Which drug can cause magnesium deficiency?

A

Proton pump inhibitors

Cytotoxic drugs

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29
Q

What are the causes of hypocalcaemia with low PTH?

A 
Genetic disorders
Post-surgery
Autoimmune
Infiltration
Radiation-induced damage to PT gland
Hungry bone syndrome
HIV infection
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30
Q

What is hypoparathyroiditis?

A

hypocalcaemia with low PTH

31
Q

What is High PTH with hypocalcaemia?

A

Secondary hyperparathyroidism in response to hypocalcaemia

32
Q

Which drugs can cause hypocalcaemia?

A 
Bisphosphonates
Calcitonin
Calcium chelators
Phenytoin 
Fluoride poisoning
33
Q

What are the causes of High PTH with hypocalcaemia?

A 
Vitamin D deficiency
Pseudohypoparathyroidism
Low Mg2+
Renal disease
Acute pancreatitis
Alkalosis
34
Q

Which investigations would you perform on a patient with suspected hypocalcaemia?

A 
ECG
Ca2+, Mg2+
Albumin
Phosphate
Vitamin D
PTH
U+E
(Neck scars)
35
Q

What would you check first in a hypocalcaemic patient?

A

PTH

36
Q

How does pseudohypoparathyroidism present?

A 
Childhood
Short 4th 5th metacarpal
Hypocalcaemia
Hyperphosphatemia
ELEVATED PTH
37
Q

How does pseudohypoparathyroidism differ from hypoparathyroidism?

A

Hypoparathyroidism has DEPRESSED PTH with the same symptoms

38
Q

What is Albright’s Heriditary Osteodystrophy?

A

Obesity
Short stature
Shortened metacarpals
May or may not have abnormal PTH/Ca2+

39
Q

What is pseudohypoparathyroidism?

A

Hypoparathyroidism characterised by target organ unresponsiveness to PTH

40
Q

What is the treatment for mild (asymptomatic) hypocalcaemia?

A

Oral Ca2+
Post-thyroidectomy - repeat Calcium 24hrs later
Fix deficiencies

41
Q

What is the treatment for severe hypocalcaemia?

A

IV calcium gluconate
ECG monitoring
Treat underlying cause

42
Q

When should vitamin D supplements be taken?

A

Winter months

October - March

43
Q

How much vitamin D should be supplemented?

A

10mcg

400 units

44
Q

When does acute hypercalcaemia require urgent correction? Why?

A

> 3.5

Risk of dysrhythmia

45
Q

What are the parathyroid mediated causes of hypercalcaemia?

A

Primary hyperparathyroidism
MEN
Familial hypocalciuric hypercalcaemia
Tertiary hyperparathyroidism (renal failure)

46
Q

What are the non-parathyroid mediated causes of hypercalcaemia?

A

HYPERCALCAEMIA OF MALIGNANCY
Vitamin D intoxication
Chronic granulomatous disorders

47
Q

What are the causes of chronic granulomatous disorders?

A

Sarcoid
TB
Berylliosis
Histioplasmosis

48
Q

Which drugs increase the risk of hypercalcaemia?

A

Thiazide diuretics
Lithium
Excess Vitamin A
Theophylline

49
Q

Which conditions can cause hypercalcaemia?

A

Hyperthyroidism
Acromegaly
Pheochromocytoma
Adrenal insufficiency

50
Q

What are the clinical features of hypercalcaemia?

A 
Bones, Stones, Groans and psychic moans
Polyuria/dipsia
Anorexia
N+V 
Muscle weakness
Shortened QT interval
51
Q

Which investigations would you use for suspected hypercalcaemia?

A 
PARATHYROID HORMONE
Albumin
U+E, Ca2+
PO4
Alk phos
Serum ACE
Myeloma screen
ECG
52
Q

What must you ALWAYS check when checking Calcium?

A

Albumin - then correct for differences

53
Q

What is the most likely cause of Normal/raised PTH with hypercalcaemia?

A

Primary hyperparathyroidism

Tertiary hyperparathyroidism

54
Q

What is the most likely cause of low PTH and hypercalcaemia?

A

Malignancy

Drugs

55
Q

Primary hyperparathyroidism is most common in which patients?

A

Female (3:1)

50-60y

56
Q

What are the biggest causes of primary hyperparathyroidism?

A

85% Parathyroid adenoma

15% four gland hyperplasia

57
Q

How should you investigate primary hyperparathyroidism?

A 
Ca, PTH
U+E
AXR - renal calciuli
DEXA - osteoporosis
Parathyroid ultrasound
Sestamibi scan
Vitamin D
24hr urine Ca2+
58
Q

What are the indications for surgery in primary hyperparathyroidism?

A 
Symptoms
Serum calcium >0.25 over upper limit (2.85)
Osteoporosis
Kidney stones/GFT<60
>50 years
59
Q

What is the medical management of primary hyperparathyroidism?

A

Fluids

Cinacalcet

60
Q

How does Familial Hypocalciuric Hypercalcaemia present?

A

Hypercalcaemia
PTH normal/raised
Positive family history
Benign

61
Q

What is Familial Hypocalciuric Hypercalcaemia?

A

Autosomal dominant disorder of the calcium sensing receptor

62
Q

What is the most common causal agent of Hypercalcaemia of malignancy?

A

Cytokines

PTHrP

63
Q

What are the most common types of hypercalcaemia of malignancy?

A

Humoural - 80%

Local osteolytic - 20%

64
Q

Which tumours typically cause Humoral Hypercalcaemia of malignancy?

A

Squamous cell cancer
Renal
Ovarian/Endometrial
Breast

65
Q

Which tumours typically cause local osteolytic Hypercalcaemia of malignancy?

A

Breast
Multiple myeloma
Lymphoma

66
Q

How does Multiple Endocrine Neoplasia type 1 present?

A

Primary hyperparathyroidism (95%)
Pancreatic
Pituitary
MENIN mutation

67
Q

What part of the investigation is especially important in patients with primary hyperparathyroidism?

A

Family history

68
Q

How does Multiple Endocrine Neoplasia type 2 present?

A

Medullary thyroid cancer
Phaeochromocytoma
Primary hyperparathyroidism (20-30%)
RET mutation

69
Q

How is hypercalcaemia managed?

A

Rehydration - monitor for fluid overload
?Dialysis
IV BISPHOSPHONATES

70
Q

What must be taken into consideration if giving a patient bisphosphonates?

A 
Do it after rehydration
(Zolendronic acid)
Give slowly in renal failure
Calcium takes 2-4 days to stabilise 
(calcitonin if these fail)
71
Q

When is parathyroidectomy indicated in hypercalcaemia?

A

Acute presentation of primary severe hypercalcaemia and poor response to other measures

72
Q

What are the causes of hypocalcaemia with high PTH?

A 
Vitamin D deficiency
Pseudohypoparathyroidism
Hypomagnesemia
Renal disease
Acute pancreatitis
Acute respiratory alkalosis
73
Q

Which drugs are associated with hypocalcaemia?

A

Bisphosphonates
Calcitonin
Cinacalcet
Phenytoin

D&E Pathology (18 decks)

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