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Endocrinology > Calcium and Bone Tutorial > Flashcards

Calcium and Bone Tutorial Flashcards

1
Q

what nakes up bone

A

collagen (protein) calcium phosphate

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2
Q

what are the component forms of bone

A

trabecular - porous sponge like

cortical bone- dense, forms outside of bones

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3
Q

what is the mineral that adds strength to bones

A

calcium phosphate

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4
Q

what hormones regulate calcium

A

parathyroid hormone

calcitonin - a polypeptide

vitamin D - from diet and sunlight

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5
Q

what does the parathyroid gland sense in relation to calcium

A

senses calcium levels via calcium sensing receptors

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6
Q

what secretes calcitonin

A

parafollicular C cell within the thryoid gland

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7
Q

where is vitamin D activated

A

by enzymes within the liver and kidneys

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8
Q

what is the role of calcium

A

maintaining bone strength
excitability of smooth and cardiac muscle
secretion of peptides and hormones in the body
excitability of skeletal neuromuscular junctions
role in blood clotting

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9
Q

what is the primary controller of calcium levels in the body

A

parathyroid hormone

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10
Q

what stimulates PTH

A

hypocalcaemia

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11
Q

what is the function of PTH

A

increase serum calcium and phosphate

activates vit D within the kidney

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12
Q

what is the action of PTH on bone

A

increases osteoclast activity within bones causing increased resorption of bone and calcium to be released

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13
Q

what is PTHs action on the kidney

A

increased tubular resorption of calcium, increasing serum levels

increases the excretion of phosphate in urine

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14
Q

what is the active for of vitamin D

A

1,25 di-OH cholecalciferol

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15
Q

what is the role of vitamin D

A

maintains mineralisation of bone in the body

helps absorption of Ca2+ and PO43 in the intestines

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16
Q

when is calcitonin released

A

in extreme cases of hypercalcaemia

17
Q

what is the role of calcitonin

A

decreases serum calcium within the body

18
Q

what effect does deficiency or excess of calcitonin have on bone health

A

none

19
Q

how does calcitonin work

A

inhibits osteoclasts, decreasing bone resorption and lowering serum calcium

lowers levels of calcium and PO43- by decreasing absorption in the intestines

decreases resorption within the kidneys - Ca2+ and PO43- is excreted in urine

increased calcium movement from plasma to bone

20
Q

what are the consequences of hypercalcaemia

A

stones, bones, moans and abdominal groans:

  • increased stimulation of smooth muscles, nerves and the heart
  • tiredness, confusion, depression
  • kidney stones
  • arrhythmias
  • muscle weakness
  • constipation
21
Q

what are the consequences of hypocalcaemia

A

increased excitability of skeletal muscle- tetany of muscles, cramps
pins and needles in hands, feet and lips
contraction of respiratory muscles - asphyxiation

22
Q

what results from hyperparathyroidism

A 
hypercalcaemia 
increased activity of osteoclasts 
osteoporosis - fractures
low serum phosphate levels due to reabsorption of calcium in kidneys 
renal stones
23
Q

what are the subtypes of hyperparathyroidism

A

primary, secondary and tertiary

24
Q

what is primary hyperparathyroidism caused by

A

overactivity of parathyroidgland

25
Q

what is secondary hyperparathyroidism caused by

A

physiological response to low calcium (PTH raised, calcium low)

26
Q

what is tertiary hyperparathyroidism caused by

A

parathyroid gland becomes autonomous after many years of secondary

27
Q

what can diagnose primary hypercalcaemia (the most common cause)

A

raised serum calcium
raised serum PTH
increased urine calcium excretion

28
Q

what is the treatment for hyperparathyroidism

A

surgery to remove adenoma causing hypersecretion (only if patient has renal stones, renal impairment or severe osteoporosis)

high fluid intake

avoid vit D and calcium high diet

29
Q

what causes hypoparathyroidism

A

lack of cells within the parathyroid gland that can secrete PTH

  • de george = congenital absence of PT glands
  • destruction via malignancies
  • autoimmune disease- destruction of parafollicular cells
30
Q

what will be seen in blood serums for hypoparathyroidism

A

hypocalcaemia and hyperphosphataemia

31
Q

what are the signs of hypoparathryoidism

A

signs of hypocalcaemia:
-chvostek sign (twitching of the face muscle when face nerve gently tapped)
-trousseaus sign- inflammation of the blood pressure cuff over systolic will cause tetany of the muscles in the hand and wrist
although increased bone calcium and density fractures still high as abnormal

32
Q

what would serum levels in hypoparathyroidism be like

A

decreased PTH
decreased calcium
increased PO43-

33
Q

what is the treatment for hypoparathyroidism

A

calcium and vitamin D supplements

34
Q

what causes pseudohypoparathyroidism

A

genetic receptor abnormality leading to resistance of the PTH hormone in the body

35
Q

what are serum levels like in pseudohypoparathyroidism

A

high PTH
decreased calcium
increased PO43-

36
Q

what are the complications of pseudohypoparathyroidism

A 
subcutaneous calcification 
mental retardation
blunting of the 4th metacarpal 
obesity 
bone abnormalities
37
Q

what can cause lack of vit D

A 
lack of sunlight absorption (winter months, skin pigment, not outdoors enough)
lack of absorption of the prehormone- poor diet, malabsorption (coeliac)
liver failure (stops activation)
38
Q

what does lack of vitamin D do

A

decreases Ca2+ and PO4s absorption within the intestine

PTH secretion will be increased as a result

lack of bone mineralisation

39
Q

what are the complications of vit d deficiency

A

rickets and craniotabes (tenderness of the skull presents as neonatal rickets) and widened epiphyses at the wrists and abnormalities in the costochondral joints (these all in children)

in adults: osteomalacia- due to lack of mineralisation bones soften becoming more likely to fracture. will have bone and muscle pain. gait deformities may occur due to proximal myopathy

Endocrinology (46 decks)

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