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Year 5 Pathology Revision > 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
describe the response to hypocalcaemia
hypocalcaemia detected by parathyroid glands release PTH calcium from - bone, gut, kidneys (and 1 alpha hydroxyls activation)
26
what is the rate limiting step in vitamin D activation
1 a hydroxylase
27
role of PTH
liberation of calcium from bone and kidneys stimulates 1 a hydroxyls activity - calcitriol stimulates renal phosphate excretion
28
role of calcitriol (1,25 (OH)2 D3)
increased calcium and phosphate absorption from the gut | bone remodelling
29
describe vitamin D synthesis
7 - dehydrocholesterol (+sun) cholecalciferol (D3) (+25 hydroxylase in liver) 25-hydroxycholecalciferol (+ 1 a hydroxylase from kidneys) 1,25 dihydroxycholecalciferol
30
why can you get hypercalcaemia in sarcoidosis
lung can express 1 alpha hydroxylase
31
what are the roles of active vitamin D
increase intestinal Ca absorption increase intestinal phosphate absorption boen formatie
32
when are ALP levels raised
by -product of osteoblast activity | levels rise when bone resorption is stimulated by vitamin D or PTH
33
features of vitamin D deficiency bone disorders
defective bone mineralisation children - rickets adults - osteomalacia
34
features of osteomalacia
bone and muscle pain increased fracture risk low calcium, low phosphate, high ALP losers zones (pesudofractures)
35
features of rickets
bowed leges costochondral swelling widened epiphyses at wrists myopathy
36
other causes of osteomalacia
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
features of osteoporosis
``` 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
T and Z score values for osteoporosis and osteopenia
osteoporosis - T score
39
list causes of osteoporosis
``` sedentary lifestyle alcohol low BMI hyperprolactinaemia thyrotoxicosis bushings steroids prolonged recurrent illness ```
40
treatment for osteoporosis
vitamin D bisphosphonates teriparatide (PTH derivative)
41
what is the most common cause of hypercalacemia
parathyroid adenoma parathyroid hyperplasia (MEN1) parathyroid carcinoma (all primary hyperparathyroidism)
42
features of familial benign hypercalcaemia
``` 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
list 3 types of hypercalacemia of malignancy
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
list causes of non-PTH driver hypercalacemia
``` sarcoidosis thyrotoxicosis (thyroxine increases bone resorption) hypoadrenalism thiazide diuretics excess vitamin D ```
45
treatment for hypercalcaemia
fluids bisphosphonates treat underling cause
46
primary cause of secondary hyperparathyroidism
``` renal osteodystrophy low/n Ca high PO4 high PTH high alk phos normal vitamin D ```
47
cause of tertiary hyperparathyroidism
``` autonomous PTH secretion post renal transplant high Ca low PO4 high PTH high/n alk phos normal vit D ```
48
causes of hypoparathyroidism
low levels pTH - primary Di George secondary - post thyroid surgery low Ca high PO4 low/n alk phos normal vit D
49
hypercalacemia - low/n albumin - high phosphate, causes?
high alp - bone mets, thyrotoxicosis, sarcoidosis normal alp - myeloma, excess vitami D, sarcoid, milk alkali
50
cause of hypercalcaemia high albumin
urea high = dehydration
51
cause of hypocalcaemia normal/ low phosphate
osteomalacia acute pancreatotos over hydration resp alkalosis
52
cause of hypocalcameia with high phosphate
CKD hypoparathyroidism (inc post thryroid surgery) pseudohyperparathyroisim hypomagnesaemia
53
symptoms of hypocalcaemia
perioral paraesthesia, carpopedal spasm, nm excitability, T+ C sign
54
treatment for hypocalacemia
oral calcium supplement eg sandocal CKD 0 alfacalcidiol severe - 10% calcium gluconate, then calcium infusion

Year 5 Pathology Revision (106 decks)

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