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2 Endocrine > Calcium and Bone Tutorial > Flashcards

Calcium and Bone Tutorial Flashcards

1
Q

what 2 substances make up most of bone?

A

calcium phosphate

collagen

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2
Q

which is the more dense of trabeclar and cortical bone?

A

cortical

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3
Q

what is the general weight of total body calcium?

A

1.5kg

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4
Q

what are the 3 main compartments of body calcium?

A

extracellular
intracellular
skeleton

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5
Q

what compartment contains plasma calcium?

A

extracellular

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6
Q

what secretes calcitonin?

A

parafollicular C cells in the thyroid gland

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7
Q

where are the enzymes located that activate Vitamin D?

A

liver

kidneys

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8
Q

what level of calcium in the body would trigger PTH?

A

(low) hypocalcaemia

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9
Q

main functions of PTH?

A

increase serum Ca
decrease serum phosphate
activate vitamin D in kidney

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10
Q

what kind of bone cell does PTH activate to cause resorption of bone and Ca?

A

osteoclast

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11
Q

what does PTH do to the kidneys to increase Ca and decrease phosphate?

A

makes them undergo tubular resorption

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12
Q

where is vitamin D synthesised?

A

intestine

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13
Q

main role of vitamin D?

A

increases kidney absorption

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14
Q

what 2 components make up vitamin D?

A

dehydrocholesterol from UV light

diet

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15
Q

when is the only time that calcitonin is secreted?

A

only in extreme hypercalcaemia

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16
Q

what is the main action of calcitonin?

A

decrease serum Ca

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17
Q

how does calcitonin decrease serum Ca?

A

inhibits osteoclasts to decrease bone resorption AND decreases tubular resorption

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18
Q

which substance has an opposing role to PTH?

A

calcitonin

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19
Q

what areas of the body are stimulated in hypercalcaemia?

A

smooth muscle
heart
nerves
ALL INCREASE

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20
Q

why do patients with hypercalcaemia get kidney stones?

A

increased levels of Ca in blood form stones with a high Ca content

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21
Q

why do you get arrhythmias in hypercalcaemia?

A

increased excitability of the heart due to increased serum Ca

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22
Q

why do patients get muscle weakness in hypercalcaemia?

A

although pts get stimulated smooth muscle, skeletal muscle is understimulated so they become weak

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23
Q

what GI complaint is common of hypercalcaemia patients?

A

constipation

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24
Q

what type of muscle is stimulated in hypocalcaemia? what are the symptoms of this

A

skeletal

tetany/cramp/pins and needles

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25
Q

why are patients more prone to osteoporosis in hyperparathyroidism?

A

PTH increases osteoclasts which break down bone

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26
Q

commonest cause of raised Ca?

A

primary hyperparathyroidism

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27
Q

3 findings needed for a diagnosis of primary hyperparathyroidism?

A

raised serum Ca
raised PTH
raised urine Ca excretion

28
Q

most common cause of primary hyperparathyroidism?

A

adenoma of the parathyroid gland

29
Q

management of hyperparathyroidism?

A

high fluid intake
low Ca/vit D diet
surgery of adenoma if serious symotoms

30
Q

why do patients get hypoparathyroidism?

A

lack of cells secreting PTH

31
Q

what is di george syndrome?

A

condition causing congenital absence of the parathyroid glands

32
Q

how can autoimmune disease cause hypoparathyroidism?

A

destructs parafollicular cells

33
Q

what is chvosteks sign?

A

twitching of the facial muscle when gentle tapping is applied to the facial nerve

34
Q

what is trousseau’s sign?

A

inflated blood pressure cuff causes tetany of the muscles of the hand and wrist

35
Q

why are hypoparathyroid patients still at a high fracture risk?

A

lack of bone remodelling due to low PTH

36
Q

treatment for hypoparathyroidism?

A

calcium/vit d supplements

37
Q

cause of pseudohypoparathyroidism?

A

genetic receptor abnormality leading to resistance of PTH

38
Q

why are PTH levels high in pseudohypoparathyroidism?

A

more is made to try to gain a response

39
Q

what hand abnormality is seen in pseudohypoparathyroidism?

A

blunting of digit 4

40
Q

what 2 problems can stop vitamin D from being ACTIVATED and why?

A

liver/kidney failure as these are where the enzymes that activate it are

41
Q

what happens to PTH levels when vitamin D is low?

A

will increase to maintain normal serum Ca

42
Q

why can bone become soft?

A

low vitamin D causes lack of mineralisation of bone

43
Q

how can you tell osteomalacia and rickets apart?

A

bone is NOT deformed

DO have a gait abnormality due to proximal myopathy

44
Q

what does a T score in a DEXA scan compare?

A

bone mineral density to the mean result of a young adult female population

45
Q

what does a Z score in a DEXA scan do?

A

mean bone mineral density compared to females of the same age

46
Q

what BMD values indicate osteopenia?

A

> 1 but under 2.5 standard deviations below the young adult mean

47
Q

what BMD values indicate osteoporosis?

A

> 2.5 standard deviations below the young adult mean

48
Q

oily fish is rich in what vitamin?

A

D

49
Q

what further investigations should be done into osteoporosis to figure out the cause?

A 
bone biochem
coeliac antibodies
protein electrophoresis
PTH levels
testosterone
50
Q

is weight bearing or non weight bearing exercise better for osteoporosis?

A

weight bearing (preserves bone density)

51
Q

what do bisphosphonates do?

A

anti-resorptive ie they inhibit osteoclast activity

52
Q

main bisphosphonate taken by patients?

A

alendronate

53
Q

effect of an addisonian crisis on Na and K?

A

low Na

high K

54
Q

what should always be in the differential for someone with tachycardia and hypotension?

A

sepsis

55
Q

what 3 things are used to manage an addisonian crisis?

A

glucose
IV fluids
steroid replacement eg hydrocortisone

56
Q

main iatrogenic cause of an addisonian crisis?

A

taking a patient immediately off a long term steroid course

57
Q

when is the only time that a short synacthen test would be inaccurate?

A

immediately post acute pituitary apoplexy

58
Q

what are sick day rules?

A

if the patient is ill one day they should double their dose for that day

59
Q

why does a lesion in the pituitary stalk cause increased prolactin?

A

inhibits dopamine transmission from the hypothalamus

60
Q

why would you experience postural hypotension in hypopituitarism?

A

lack of ACTH release stops mineralocorticoid (eg aldsterone) production

61
Q

what would TFTs look like in someone with hypopituitarism?

A

low or normal TSH

low T4

62
Q

why are T4 levels low in hypopituitarism?

A

lack of TSH from the pituitary

63
Q

commonest cause of hypopituitarism?

A

pituitary tumour

64
Q

infective causes of hypopituitarism?

A

meningitis
syphilis
encephalitis

65
Q

treatment for hypopituitarism?

A

HRT eg thyroxine, steroids, testosterone

66
Q

what is TRAB?

A

TSH receptor antibodies

2 Endocrine (35 decks)

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