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Year 5 path SW > Chempath 10: Calcium > Flashcards

Chempath 10: Calcium Flashcards

1
Q

Where does PTH act ?

A
  • Kidneys directly (increased Ca reabsorption, increased PO4 excretion)
  • Increases 1 alpha hydroxylase
  • Bone (causes increased Ca and PO4 resorption)
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2
Q

What does 1° alpha hydroxylase do ?

A

Activates vitamin D 25-OH-D3 –> 25- (OH)2-D3

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3
Q

What is the most common cause of 1° hyperparathyroidism?

A

Parathyroid adenoma

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4
Q

What causes 2° hyperparathyroidism ?

A

Renal osteodystrophy

(chronic renal failure means less vitamin D activated, so less Ca resorption and less PO4 excretion. low calcium causes PTH release)

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5
Q

What causes 3° hyperparathyroidism ?

A

Prolonged CKD in 2° hyperparathyroidism causes hyperplasia of the Parathyroid causing autonomous PTH release even when Ca is high.

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6
Q

List 2 causes of hypoparathyroidism ?

A

1- Di George syndrome

2- Post thyroidectomy

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7
Q

What does vitamin D deficiency cause ?

A

Rickets in children

Osteomalacia in adults

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8
Q

Which metabolic bone disorder causes looser’s zone fractures and bowing ?

A

Osteomalacia

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9
Q

What happens in Paget’s disease?

A

Increased bone remodelling

high PTH

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10
Q

How can sarcoidosis cause hypercalcaemia ?

A

causes non-renal release of 1 alpha hydroxylase

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11
Q

What are the features of Pseudohypoparathyroidism?

A
  • Type 1a = Albright’s hereditary osteodystrophy
  • High PTH, low Ca, High PO4
  • PTH resistance means low calcium
  • syndromic features: low IQ, short stature, short 4th and 5th metacarpals
  • Maternal imprinting of an autosomal dominant mutation
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12
Q

What are the features of pseudopseudohypoparathyroidism ?

A
  • same syndromic features as Albright’s hereditary osteodystrophy
  • Calcium is normal because no PTH resistance
  • Paternal imprinting of autosomal dominant mutation
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13
Q

What is the management of hypercalcaemia?

A

1- Hydration with fluids
2- Bisphosphonates
3- Calcitonin (severe)

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14
Q

What is the management of hypocalcaemia ?

A

1-Give calcium
CKD: Alpha calcidiol
3- 10% Calcium gluconate IV

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15
Q

Why can Chronic pancreatitis cause Osteomalacia ?

A
  • Chronic pancreatitis causes a reduction in emulsification of fats
  • This means less fat soluble vitamins (ADEK) are absorbed from the G.I tract
  • Causing a vitamin D deficiency and therefore osteomalacia
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16
Q

Why does Multiple Myeloma not cause a raised ALP ?

A
  • Multiple myeloma only affects osteoclasts

- Osteoblast activity is what releases ALP

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17
Q

List 4 causes of a raised ALP?

A
  • Cholestatic liver disease (also raised GGT)
  • Pregnancy (Placenta releases ALP)
  • Bone disease (Paget’s, Renal osteodystrophy fracture)
  • Drugs (carbamazepine, phenytoin, erythromycin)
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18
Q

Why do we use corrected calcium ?

A

-Because normally 40% of calcium is bound to albumin, so if anything affects albumin it would also affect calcium levels.

Corrected calcium takes albumin into consideration

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19
Q

List 3 causes of hypocalcaemia with elevated phosphate ?

A
  • CKD
  • Hypoparathyroidism
  • Hypomagnesaemia
  • (Pseudohypoparathyroidism)
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20
Q

List 3 causes pf Hypocalcaemia with normal or low phosphate ?

A
  • Osteomalacia
  • Acute pancreatitis
  • Respiratory alkalosis
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21
Q

Why does respiratory alkalosis cause Hypocalcaemia ?

A
  • Respiratory alkalosis is most commonly due to hyper ventilation.
  • The alkalosis causes increased binding of free calcium to albumin.
  • Less free calcium causes hypocalcaemia seen with symptoms such as parasthesia, tetany etc
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22
Q

normal calcium concentration

A

2.2-2.6 mmol/L

23
Q

forms of calcium in the serum

A

free (ionised) - 50% - BIOLOGICALLY ACTIVE
protein-bound - 40% - bound to albumin
complexed - 10% - citrate/phosphate

24
Q

why do you measure corrected calcium

A

takes into account the serum albumin

25
Q

describe the response to hypocalcaemia

A

hypocalcaemia detected by parathyroid glands
release PTH
calcium from - bone, gut, kidneys (and 1 alpha hydroxyls activation)

26
Q

what is the rate limiting step in vitamin D activation

A

1 a hydroxylase

27
Q

role of PTH

A

liberation of calcium from bone and kidneys
stimulates 1 a hydroxyls activity - calcitriol
stimulates renal phosphate excretion

28
Q

role of calcitriol (1,25 (OH)2 D3)

A

increased calcium and phosphate absorption from the gut

bone remodelling

29
Q

describe vitamin D synthesis

A

7 - dehydrocholesterol (+sun)
cholecalciferol (D3) (+25 hydroxylase in liver)
25-hydroxycholecalciferol (+ 1 a hydroxylase from kidneys)
1,25 dihydroxycholecalciferol

30
Q

why can you get hypercalcaemia in sarcoidosis

A

lung can express 1 alpha hydroxylase

31
Q

what are the roles of active vitamin D

A

increase intestinal Ca absorption
increase intestinal phosphate absorption
boen formatie

32
Q

when are ALP levels raised

A

by -product of osteoblast activity

levels rise when bone resorption is stimulated by vitamin D or PTH

33
Q

features of vitamin D deficiency bone disorders

A

defective bone mineralisation
children - rickets
adults - osteomalacia

34
Q

features of osteomalacia

A

bone and muscle pain
increased fracture risk
low calcium, low phosphate, high ALP
losers zones (pesudofractures)

35
Q

features of rickets

A

bowed leges
costochondral swelling
widened epiphyses at wrists
myopathy

36
Q

other causes of osteomalacia

A

renal failure - lack of 1 a hydroxylase means you cannot activate vitamin D (can give pre-activates)

anticonvulsants (bd vitamin D)

physic acid - chelates vitamin D, chapatis

37
Q

features of osteoporosis

A 
fractures preset 
loss of bone mass
disuse of bones
collie's fracture (wrist), hip, spine
calcium and phosphate normal

DEXA scan - T score, Z score

38
Q

T and Z score values for osteoporosis and osteopenia

A

osteoporosis - T score

39
Q

list causes of osteoporosis

A 
sedentary lifestyle
alcohol 
low BMI 
hyperprolactinaemia
thyrotoxicosis
bushings 
steroids
prolonged recurrent illness
40
Q

treatment for osteoporosis

A

vitamin D
bisphosphonates
teriparatide (PTH derivative)

41
Q

what is the most common cause of hypercalacemia

A

parathyroid adenoma
parathyroid hyperplasia (MEN1)
parathyroid carcinoma

(all primary hyperparathyroidism)

42
Q

features of familial benign hypercalcaemia

A 
caused by a mutation in the CaSR 
this detect calcium levels 
increase in the set point for PTH release
causes mild hypercalcaemia 
benign 
no kidney stones
43
Q

list 3 types of hypercalacemia of malignancy

A

humour hypercalcaemia of malignant (eg small cell lung cancer) - PTHrp release

bone mets - eg breast cancer - local bone osteolysis

haem malignancy - eg myeloma - cytokines

44
Q

list causes of non-PTH driver hypercalacemia

A 
sarcoidosis 
thyrotoxicosis (thyroxine increases bone resorption)
hypoadrenalism 
thiazide diuretics 
excess vitamin D
45
Q

treatment for hypercalcaemia

A

fluids
bisphosphonates
treat underling cause

46
Q

primary cause of secondary hyperparathyroidism

A 
renal osteodystrophy 
low/n Ca
high PO4
high PTH 
high alk phos
normal vitamin D
47
Q

cause of tertiary hyperparathyroidism

A 
autonomous PTH secretion post renal transplant 
high Ca
low PO4 
high PTH
high/n alk phos
normal vit D
48
Q

causes of hypoparathyroidism

A

low levels pTH - primary Di George
secondary - post thyroid surgery

low Ca
high PO4
low/n alk phos
normal vit D

49
Q

hypercalacemia - low/n albumin - high phosphate, causes?

A

high alp - bone mets, thyrotoxicosis, sarcoidosis

normal alp - myeloma, excess vitami D, sarcoid, milk alkali

50
Q

cause of hypercalcaemia high albumin

A

urea high = dehydration

51
Q

cause of hypocalcaemia normal/ low phosphate

A

osteomalacia
acute pancreatotos
over hydration
resp alkalosis

52
Q

cause of hypocalcameia with high phosphate

A

CKD
hypoparathyroidism (inc post thryroid surgery)
pseudohyperparathyroisim
hypomagnesaemia

53
Q

symptoms of hypocalcaemia

A

perioral paraesthesia, carpopedal spasm, nm excitability, T+ C sign

54
Q

treatment for hypocalacemia

A

oral calcium supplement eg sandocal
CKD 0 alfacalcidiol
severe - 10% calcium gluconate, then calcium infusion

Year 5 path SW (106 decks)

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