Calcium Dysregulation

Question 1

What hormone(s) increases calcium levels?

Answer 1

Vitamin D

Parathyroid hormone

Question 2

What hormone(s) decreases calcium levels?

Answer 2

Calcitonin

Question 3

How is vitamin D mentabolised?

Answer 3

UVB light
7 dehydrocholesterol
Pre vitamin D3
Vitamin D3
OR
Vitamin D2 from diet
25 hydroxylase in liver makes it 25(OH) cholecalciferol
1 alpha hydroxylase in kidney makes it 1,25 dihydroxy cholecalciferol= calcitriol

Question 4

What is the active form of vitamin D called?

Answer 4

Calcitriol

Question 5

What vitamin D enzyme is found in the liver?

Answer 5

25 hydroxylase

Question 6

What vitamin D enzyme is found in the kidney?

Answer 6

1 alpha hydroxylase

Question 7

What are the effects of calcitriol?

Answer 7

Effects bone, kidney and gut
Increases osteoblast activity (vit D for bone strength)

Works to increase calcium by increasing calcium absorption by bone

Increases Ca2+ reabsorption from kidney and gut
Increases phosphate reabsorption from kidney and from gut

Question 8

What are the effects of PTH?

Answer 8

Increases calcium reabsorption from bone
Increases calcium reabsorbtion from gut and kidney
Increases phosphate absorbtion from gut
Increases phosphate excretion in the kidney
Increases 1 alpha hydroxylase activity in kidney

Question 9

What does FGF23 do?

Answer 9

Blocks sodium phosphate co transporter in PCT, encouraging excretion of phosphate in the urine
It also inhibits calcitriol
This leads to less phosphate reabsorption from gut

Question 10

What is calcitriol inhibited by?

Answer 10

FGF23

Question 11

How does hypocalcaemia present?

Answer 11

Cats go numb:
Convulsions
Arrythmias
Tetany
Paraesthesia

Question 12

What are the 2 signs of hypocalcaemia?

Answer 12

Chovstek’s sign- facial paraesthesia when you tap the zygomatic branch of the facial nerve
Trousseau’s sign- carpopedal spasm

Question 13

What are the causes of hypocalcaemia?

Answer 13

Low PTH levels (surgical, autoimmune, magnesium deficiency, congenital)
Low vitamin D (diet deficiency, UV light etc)

Question 14

How does hypercalcaemia present?

Answer 14

Stones- renal effects (nephrocalcinosis: kidney stones)
Abdominal moans- GI effects (anorexia, nausea, dyspepsia, constipation, pancreatitis)
Psychic groans- CNS effects (fatigue, depression, impaired concentration, altered mentation, coma)

Question 15

What are the causes of hypercalcaemia?

Answer 15

Primary hyperparathyroidism- too much PTH
Malignancy- produce local factors to activate osteoclasts or make peptide that acts on PTH receptors
Vitamin D excess

Question 16

What is the normal relationship between calcium and PTH? Describe why this relationship arises

Answer 16

As calcium falls, PTH rises

This is because PTH increases levels of calcium so is only released when calcium levels are low

Question 17

Describe what happens in primary hyperparathyroidism and what the hormone levels are

Answer 17

Parathyroid gland adenoma resulting in excess PTH secretion,
hypercalcaemia and high PTH

Question 18

Describe what happens in secondary hyperparathyroidism and what the hormone levels are

Answer 18

Vitamin D deficiency (due to lack in diet or no sunlight) leading to excess PTH to compensate, low calcium, high PTH, low vit D

Question 19

Describe what happens in tertiary hyperparathyroidism and what the hormone levels are

Answer 19

Complication of renal failure, unable to make calcitriol so parathyroid glands become hyperplasic and make lots of PTH, high PTH, low vit D, high calcium

Question 20

How is primary hyperparathyroidism treated?

Answer 20

Parathyroidectomy/tumor removal

Question 21

How is secondary hyperparathyroidism treated?

Answer 21

Vitamin D supplements (25 hydroxy vitamin D)`

Question 22

How is tertiary hyperparathyroidism treated?

Answer 22

Parathyroidectomy

Question 23

What is calcium resorption? How does it affect calcium levels?

Answer 23

The process of removing old bone tissue via osteoclasts and laying down new bone tissue via osteoblasts, it increases calcium levels

Question 24

What is the difference between calcitonin and calcitriol?

Answer 24

Calcitriol is the active form of vitamin D

Calcitonin is a hormone that reduces levels of calcium

Question 25

What are the 2 ways we can take in vitamin D? What specific type of vitamin D is associated with each?

Answer 25

Sunlight- this involves vitamin D3

Diet- this involves vitamin D2

Question 26

What are calcium, phosphate and PTH levels in primary hyperparathyroidism? Explain each one

Answer 26

Calcium is high due to excess PTH
Phosphate is low as PTH causes increased renal phosphate excretion
PTH is high as it isn’t suppressed by hypercalcaemia as there is a pituitary adenoma

Question 27

What is the main difference between primary and secondary hyperparathyroidism?

Answer 27

In primary calcium is high but in secondary it is low because the high PTH is secondary to low calcium

Question 28

When taking a diagnostic approach to hypercalcaemia, what do we always have to look at?

Answer 28

PTH

Question 29

What is the normal PTH response to hypercalcaemia? When this doesn’t occur what can you suspect?

Answer 29

Normal response is for PTH to fall, this may not happen in malignancy or chronic renal failure

Question 30

If a patient presents with hypercalcaemia and high PTH what are the possible diagnoses?

Answer 30

Primary hypercalcaemia due to pituitary adenoma

Tertiary hypercalcaemia due to chronic renal failure

Question 31

What is the diagnostic approach to vitamin D deficiency?

Answer 31

Measure calcium, it will be low or low/normal
PTH should be high when measured
Measure vitamin D as 25 (OH) vitamin D

Question 32

What form of vitamin D is hard to measure?

Answer 32

Calcitriol