Calcium and phosphate regulation

Question 1

Which hormone is responsible for increasing serum calcium levels?

Answer 1

PTH

Question 2

Recall the 4 effector functions of PTH

Answer 2

1. Promotes bone resorption
2. Increases renal Ca++ reuptake
3. Increases renal Vit D phosphorylation
4. Decreases renal PO4 reuptake

Question 3

Where is phosphate reabsorbed in the kidney, and how does this happen?

Answer 3

PCT - with Na+

Question 4

By what 2 factors might PO4 reuptake be inhibited? What is the mechanism of this inhibition?

Answer 4

PTH, FGF23

Inhibits Na+/PO4— cotransporter to promote phosphaturia

Question 5

What does FGF23 stand for and what are its 2 main actions?

Answer 5

Fibroblast Growth Factor 23 - inhibits calcitriol and Na+/PO4— cotransporter

Question 6

Recall 3 possible names for active vitamin D

Answer 6

1. Calcitriol
2. 1-alpha-25-dihydroxycholecalciferol
3. 1-25-dihydroxyvitamin D3

Question 7

How is PTH secretion regulated?

Answer 7

PTH receptors on parathyroid gland have negative feedback effect when stimulated

Question 8

How does serum Ca++ affect neuromuscular exciteability?

Answer 8

HypOcalcaemia –> more Na+ influx –> hypERexciteability

HypERcalcaemia –> inhibition of Na+ flux –> hypOexciteability

Question 9

What is the normal range for serum Ca++?

Answer 9

2.2-2.6mmol/L

Question 10

What pneumonic is used to remember the signs of hypocalcaemia?

Answer 10

CATs go numb

Question 11

What are the signs of hypocalcaemia, and how can these be tested?

Answer 11

Convulsions
Arrhythmias
Tetany
Paraesthesia
Chovstek/ Trousseau's signs

Question 12

How is Chovstek’s sign performed?

Answer 12

Tap facial nerve just below zygomatic arch - pos response = twitching of facial muscles

Question 13

How is Trousseau’s sign performed?

Answer 13

Inflation of blood pressure cuff - pos response = clamping of hand

Question 14

Recall 4 possible causes of hypocalcaemia

Answer 14

Vit D deficiency
PTH deficiency
PTH resistance
Renal failure

Question 15

Recall 3 possible causes of PTH deficiency

Answer 15

1. Autoimmune
2. Neck surgery
3. Hypomagnesaemia

Question 16

What name is given to PTH resistance?

Answer 16

Pseudohypoparathyroidism

Question 17

Why might renal failure lead to vit D deficiency?

Answer 17

Loss of 1-alpha-hydroxylase

Question 18

What saying is used to remember the symptoms of hypercalcaemia?

Answer 18

stones, abdominal moans and psychiatric moans

Question 19

What is the cause of renal colic?

Answer 19

Nephrocalcinosis

Question 20

Recall 4 of the abdominal complaints associated with hypercalcaemia

Answer 20

1. Anorexia
2. Nausea
3. Constipation
4. Predisposition to pancreatitis

Question 21

What happens to serum Ca++ in hyperparathyroidism?

Answer 21

Elevated

Question 22

Recall 3 possible causes of hypercalcaemia

Answer 22

Hyperparathyroidism
Malignancy secreting PTHRP
Vit D toxicosis

Question 23

Recall the Ca++, PO4— , vit D and PTH levels in primary hyperparathyroidism

Answer 23

Ca++ = high
PO4— = low
Vit D = low
PTH = high

Question 24

Recall the Ca++, PO4— and PTH levels in hypercalcaemia of malignancy

Answer 24

Ca++ = high
PO4--- = low
PTH = low

Question 25

Recall 6 possible causes of vit D deficiency

Answer 25

1. Poor diet
2. Coeliac disease
3. Lack of UVB
4. Renal failure
5. Liver failure
6. Vit D receptor defects

Question 26

What is the cause of primary hyperparathyroidism?

Answer 26

adenoma of gland

Question 27

How does vit D promote bone resorption?

Answer 27

Promotes RANK-L expression by osteoblasts

Question 28

Recall 2 inhibitors of PTH

Answer 28

Ca++

E2