Calcium And Phosphate

Question 1

What is the acronym for the uses of Calcium?

Answer 1

MISBEN

Question 2

Where does Parathyroid Hormone act?

Answer 2

Kidneys and Bone

Question 3

What effect does PTH have on bone?

Answer 3

Increase Ca2+ resorption

Increase PO4 3- resorption

Question 4

What effect does PTH have on the Kidneys? (2)

Answer 4

1. Increase Ca2+ reabsorption, decrease PO4 3- reabsorption

2. Secretion of 1α hydroxylase

Question 5

Where is 90% of vitamin D in the body from?

Answer 5

The sun, absorbed through skin as D3

Question 6

Where is 10% of the Vitamin D in the body from?

Answer 6

Diet, in D2 form

Question 7

What effect does the liver have on vitamin D?

Answer 7

Secretes 25 hydroxylase to convert it to Calcidiol

Question 8

What effect do the kidneys have on vitamin D?

Answer 8

Secrete 1α hydroxylase (stimulated by PTH) to convert it to Calcitriol (active Vitamin D)

Question 9

Where does Calcitriol (active Vitamin D) affect?

Answer 9

Kidneys, Bone, Gut

Question 10

What does Calcitriol do to the kidneys?

Answer 10

Increase reabsorption of Ca2+ and PO4 3-

Question 11

What effect does Calcitriol have on Bone?

Answer 11

Increase Ca2+ and PO4 3- resorption

Question 12

What effect does Calcitriol have on the gut?

Answer 12

Increase Ca2+ absorption, increase PO4 3- absorption

Question 13

Where is Calcitonin produced?

Answer 13

C cells of the Thyroid gland

Question 14

What stimulates production of Calcitonin?

Answer 14

Increasing serum levels of Ca2+

Question 15

What stimulates production of PTH?

Answer 15

Decreasing levels of plasma Ca2+

Question 16

What effects does Calcitonin have?

Answer 16

Blocks effects of PTH:
Kidneys - decrease Ca2+, increase PO4 3- absorption; decrease 1α hydroxylase secretion
Bone - decrease Ca2+ and PO4 3- resorption

Question 17

Name the 6 uses of Calcium

Answer 17

Muscle Contraction
Intracellular signalling
Stabilise membrane potential
Bones + teeth
Enzyme Cofactor
Nerve function/Neurotransmission

Question 18

Where is most Calcium stored in the body?

Answer 18

Bones (99%)

Question 19

Where is the remaining body calcium found?

Answer 19

Intracellular (~1%) and Extracellular (plasma - ~01.%)

Question 20

What is Parathyroid Hormone-Related Peptide (PTHrP)?

Answer 20

Hormone that mimics PTH: produced by some cancers, and causes hypercalcaemia associated with malignancy
NB: does not increase 1,25 D3 levels

Question 21

What is FGF-23?

Answer 21

Fibroblast Growth Factor.

Predominantly made by osteocytes and osteoblasts

Question 22

What does FGF-23 do?

Answer 22

Prevents vitamin D mediated hyperphosphataemia by increasing removal via urine (phosphaturic)
Inhibits 1α hydroxylase -> decreases active levels of Vitamin D
Inhibits type II sodium phosphate co-transporters

Question 23

What are the symptoms of Hypocalcaemia?

Answer 23

Neuromuscular irritability
Muscle Cramps / Tetany
Seizures

Question 24

Why does Tetany occur in hypocalcaemia?

Answer 24

As extracellular Ca2+ falls, peripheral nerve fibres discharge spontaneously, leading to muscle contractions

Question 25

What are the symptoms of Hypercalcaemia?

Answer 25

Nausea/vomiting/constipation/anorexia
Tiredness, confusion, depression, headaches
Muscle weakness
Kidney stones
Loss of bone
Polyuria

Question 26

What can cause hypercalcaemia?

Answer 26

Primary or Tertiary Hyperparathyroidism

Question 27

What can cause Hypocalcaemia?

Answer 27

Primary and Pseudo- Hypoparathyroidism, and Secondary Hyperparathyroidism

Question 28

What is the treatment of Hypercalcaemia?

Answer 28

Fluids
Loop diuretic (e.g. Furosemide)
Calcitonin
Bisphosphonates

Question 29

What is the treatment for Hypocalcaemia?

Answer 29

Acute: IV calcium gluconate
Chronic: oral calcium + vitamin D

Question 30

What is the principle of management for hypo/hypercalcaemia?

Answer 30

Aim to restore normal Ca levels, treat any emergency symptoms, and find underlying cause