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Endocrinology > Calcium and bone > Flashcards

Calcium and bone Flashcards

1
Q

What is bone made up mostly of?

A

Collagen and calcium phosphate

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2
Q

What adds the strength to bone?

A

Calcium phosphate

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3
Q

What are the two types of bone?

A

Trabecular and cortical

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4
Q

What are the characteristics of trabecular bone?

A

Porous, sponge like bone

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5
Q

What are the characteristics of cortical bone?

A

Forms majority of the outside of bone - very dense material

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6
Q

What is bone constantly going through?

A

A remodelling process

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7
Q

What is the remodelling process a balance between?

A

Bone formation and resorption

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8
Q

What cell is responsible for bone formation?

A

Osteoblasts

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9
Q

What cell is responsible for bone resorption?

A

Osteoclasts

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10
Q

What concentrations are important in the body to maintain strong healthy bone?

A

Calcium and phosphate

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11
Q

Where is the body’s calcium found?

A

Intracellular, skeleton and extracellular

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12
Q

Where is the majority of the body’s calcium found?

A

In the skeleton

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13
Q

What three hormones are involved in the regulation of extracellular body calcium?

A

Calcitonin, parathyroid hormone and vitamin D

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14
Q

What does parathyroid hormone do?

A

Senses calcium levels within the body

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15
Q

What is calcitonin?

A

A polypeptide

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16
Q

Where is calcitonin secreted from?

A

Parafollicular C cells in thyroid gland

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17
Q

What activates vitamin D?

A

Enzymes within the liver and kidneys

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18
Q

Besides maintaining bone strength, what else is calcium essential in?

A

Excitability of smooth and cardiac muscle, secretion of peptides and hormones in body, role in blood clotting and excitability of skeletal neuromuscular junctions

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19
Q

What stimulates parathyroid hormone?

A

Hypocalcaemia

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20
Q

What are the functions of parathyroid hormone?

A

Increases serum calcium, decreases serum phosphate and activates vitamin D within the kidney

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21
Q

How does PTH increase serum calcium and decrease serum phosphate in bone?

A

Increase osteoclastic activity - causing increased resorption of bone - calcium released from labile pool of calcium phosphate

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22
Q

How does PTH increase serum calcium and decrease serum phosphate in kidney?

A

Increases resorption of calcium and causes increased secretion of phosphate in the urine

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23
Q

What needs to happen to vitamin D before it has any effect in the body?

A

Must be hydroxylated

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24
Q

How does vitamin D in its active form (steroid) work in the kidney?

A

Increases absorption resulting in increase absorption of both calcium and phosphate

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25
Q

What important role does activated vitamin D have in bone?

A

Maintaining mineralisation of bone

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26
Q

Compare the role of calcitonin and PTH/vit D in role of serum calcium?

A

Low

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27
Q

When is calcitonin secreted?

A

Extreme cases of hypercalcaemia

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28
Q

What is the action of calcitonin?

A

Decreases serum calcium

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29
Q

What effect does deficiency or excess of calcitonin have on bone?

A

Has no effect on bone quality

30
Q

How does calcitonin work in bone?

A

Inhibits osteoclasts - decreases bone resorption

Also moves calcium from plasma to labile pool of calcium phosphate

31
Q

What does decreased bone resorption mean with regards to calcium levels?

A

Extracellular calcium levels are lower

32
Q

How does calcitonin work in the intestines?

A

Decreases absorption - lowers levels of calcium and phosphate

33
Q

How does calcitonin work in the kidneys?

A

Decreases reabsorption of calcium and phosphate - increased excretion

34
Q

What are the clinical features of hypercalcaemia?

A 
Patient will feel tired, confused and depressed 
May be history of kidney stones 
Arrhythmias - ECG changes 
Muscle weakness 
Constipation 
STONES, BONES, MOANS and ABDO GROANS
35
Q

What are the clinical features of hypocalcaemia?

A

Cramp and tetany of muscles
Pins and needles in extremities
Generally those opposite to hypercalcaemia

36
Q

What is an extreme complication of hypocalcaemia?

A

Death due to asphyxiation - unrelieved contraction of rest muscles

37
Q

What are the symptoms of hyperparathyroidism?

A

Same as hypercalcaemia

However with osteoporosis - more likely to develop bone fractures

38
Q

What is the cause of primary hyperparathyroidism?

A

Overactivity off parathyroid gland

39
Q

What are the serum levels in primary hyperparathyroidism?

A

PTH raised

Ca raised

40
Q

What is the cause of secondary hyperparathyroidism?

A

Physiological response to low calcium

41
Q

What are the serum levels in secondary hyperparathyroidism?

A

PTH raised

Ca low

42
Q

What is the cause of tertiary hyperparathyroidism?

A

Parathyroid gland becomes autonomous after many years of secondary

43
Q

What are the serum levels in tertiary hyperparathyroidism?

A

PTH raised

Ca raised

44
Q

How is primary hyperparathyroidism diagnosed?

A

Achieved from finding:

  • raised serum PTH
  • raised serum calcium
  • increased urine calcium excretion
45
Q

What is the management of an adenoma causing hyperparathyroidism?

A

Surgery and removal

46
Q

When is removal of can adenoma causing hyperparathyroidism encouraged?

A

When the patient is suffering from:

  • Renal stones
  • Renal impairment
  • Severe osteoporosis
47
Q

What is the medical management of hyperparathyroidism?

A

There is none however patients are encouraged to have a high fluid diet and high calcium and fit D diet should be avoided

48
Q

What is the most common cause of primary hyperparathyroidism?

A

Adenoma of parathyroid gland

49
Q

How does hypoparathyroidism arise?

A

Lack of cells within parathyroid gland that actively secrete PTH

50
Q

What are the causes of hypoparathyroidism?

A

Di George syndrome, malignancy, autoimmune disease

51
Q

How does Di George syndrome cause hypoparathyroidism?

A

Congenital absence of parathyroid glands

52
Q

How does malignancy cause hypoparathyroidism?

A

Destruction of cells

53
Q

How does autoimmune disease cause hypoparathyroidism?

A

Autoantibodies destroy parafollicular cells

54
Q

What are the serum levels in hypoparathyroidism?

A

Low calcium
High phosphate
Little or no PTH

55
Q

What are the signs and symptoms in hypoparathyroidism?

A

Same as for hypocalcaemia as well as:

  • Chvostek’s sign
  • Trousseau’s sign
  • Higher rate of fractures due to abnormalities in bone remodelling
56
Q

What is Chvostek’s sign?

A

Twitching of facial muscle when gentle tapping is applied to facial nerve

57
Q

What is Trousseau’s sign?

A

Inflation of BP cuff over systolic pressure for a period of time will result in tetany of muscles in hand and wrist

58
Q

How is hypoparathyroidism diagnosed?

A

Blood samples of hormone and serum electrolytes

59
Q

What is the management of hypoparathyroidism

A

Calcium and vitamin D supplements

60
Q

What is pseudohypoparathyroidism?

A

Condition caused by genetic receptor abnormality - leads to resistance of PTH

61
Q

What are the serum levels in pseudohypoparathyroidism?

A

Increased PTH
decreased calcium
Increased phosphate

62
Q

Why is there an increased level of PTH in pseudohypoparathyroidism?

A

Hypocalcaemia stimulates release of even more PTH

63
Q

What are the complications of pseudohypoparathyroidism?

A

Subcut calcificano, mental retardation, blunting of fourth metacarpal, obesity and bone abnormalities

64
Q

What are the causes of a lack of bit D?

A

Lack of sunlight absorption (winter, skin pigment, indoors too much)
Lack of absorption of pre hormone (poor diet, coeliac)
Problem with activation (Liver failure, kidney failure)

65
Q

What happens in the intestines when there is a lack of vitamin D in the body?

A

Absorption of both calcium and phosphate will be decreased

66
Q

What happens in the bone when there is a lack of vitamin D?

A

Lack of mineralisation of bone - decreased bone quality as well as increased resorption (less dense and weaker)

67
Q

What is rickets?

A

Condition in children where low vitamin D levels causes bone to become soft

68
Q

What happens when there isn’t enough vitamin D in a child?

A

Legs bow as they aren’t dense enough to support weight of body

69
Q

How does neonatal rickets present?

A

Soft skull and tenderness - craniotabes

70
Q

What happens at the wrists in rickets?

A

Widened epiphyses

71
Q

What is osteomalacia?

A

Similar to rickets but in adults

72
Q

How do patients present with osteomalacia?

A

Bone and muscle tenderness
Pathological fractures
Gait deformities (proximal myopathy)

Endocrinology (6 decks)

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