Chempath 10: Calcium Flashcards Preview

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Flashcards in Chempath 10: Calcium Deck (21)
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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)
2
Q

What does 1° alpha hydroxylase do ?

A

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

3
Q

What is the most common cause of 1° hyperparathyroidism?

A

Parathyroid adenoma

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)

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.

6
Q

List 2 causes of hypoparathyroidism ?

A

1- Di George syndrome

2- Post thyroidectomy

7
Q

What does vitamin D deficiency cause ?

A

Rickets in children

Osteomalacia in adults

8
Q

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

A

Osteomalacia

9
Q

What happens in Paget’s disease?

A

Increased bone remodelling

high PTH

10
Q

How can sarcoidosis cause hypercalcaemia ?

A

causes non-renal release of 1 alpha hydroxylase

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
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
13
Q

What is the management of hypercalcaemia?

A

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

14
Q

What is the management of hypocalcaemia ?

A

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

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
16
Q

Why does Multiple Myeloma not cause a raised ALP ?

A
  • Multiple myeloma only affects osteoclasts

- Osteoblast activity is what releases ALP

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)
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

19
Q

List 3 causes of hypocalcaemia with elevated phosphate ?

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

List 3 causes pf Hypocalcaemia with normal or low phosphate ?

A
  • Osteomalacia
  • Acute pancreatitis
  • Respiratory alkalosis
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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