Calcium Dysregulation

Question 1

How is serum calcium increased and decreased?

Answer 1

Increase- vit D and PTH
Decrease- calcitonin

Question 2

How is Vit D metabolised?
What do we use to measure vit d levels?

Answer 2

UVB goes to skin = vitamin D3
Vit D3 goes to liver and becomes 25ohcholecalciferol via 25-hydroxylase (this is inactive form)
In kidney 1 alpha hydroxylase activates it to form calcitriol
We use 25 hydroxylase to measure VIT D

Question 3

What are the effects of calcitriol?

Answer 3

Increases osteoclast = increases calcium serum levels
Increases calcium and phosphate réabsorption in kidney
Increases calcium and phosphate absorption in gut

Question 4

What are the effects of pth?

Answer 4

Increases réabsorption of calcium but decreases of phosphate
Increases 1 alpha hydroxylase activity in kidney = more vit d
Increases secretion of phosphate in kidney
Increases absorption of calcium and phosphate in gut
Increases osteoblast activity

Question 5

What is the role of FGF23?

Answer 5

Hormone that decreases phosphate réabsorption in kidney
Does this by inhibiting na+/po43- co-transporter
Also inhibits calcitriol

Question 6

How does hypocalcaemia present?

Answer 6

CATS go numb (numbness in fingers)
Convulsions
Arrhythmias
Tetany (spasms of muscles)
Spasms
Paresthesia
Chvosteks sign (cheek)
Trosseaus sign (hand)

Question 7

What are the causes of hypocalcaemia?

Answer 7

Hypoparathyroidism
Neck surgery
Autoimmune
Magnesium deficiency
Poor vit d levels

Question 8

How does hypercalcaemia present?

Answer 8

Stones, abdominal groans and psychic moans
Renal stones
Nausea
Fatigue depression

Question 9

What are the causes of hypercalcaemia?

Answer 9

Primary hyperparayhyroidism- adenoma on pt gland
No neg feedback
Cancer malignancy
Vit d excess

Question 10

What are the different types of hyperparathyroidism?
How are they each treated?
What two conditions can sometimes happen as a result of this?

Answer 10

Primary: increase PTH and increase calcium but low phosphate - no neg feedback on PTH as adenoma releases the PTH. Parathyroidectomy
Secondary: normal response to low calcium, neg feedback loop causes increase PTH- can be caused by vitamin D deficiency. Give ergocalciferol or alfacalcidol if there is renal failure causing the Vit D
Tertiary: chronic renal failure = chronic vit d deficiency = decrease calcium = pt glands enlarge (hyperplasia) to point where they can’t switch off (even though calcium is normal) = hypercalcaemia = parathyroidectomy

Hypercalcaemia and osteoporosis