Calcium Dysregulation Flashcards

1
Q

What hormone(s) increases calcium levels?

A

Vitamin D

Parathyroid hormone

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2
Q

What hormone(s) decreases calcium levels?

A

Calcitonin

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3
Q

How is vitamin D mentabolised?

A
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 (OH)2 cholecalciferol= calcitriol
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4
Q

What is the active form of vitamin D called?

A

Calcitriol

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5
Q

What vitamin D enzyme is found in the liver?

A

25 hydroxylase

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6
Q

What vitamin D enzyme is found in the kidney?

A

1 alpha hydroxylase

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7
Q

What are the effects of calcitriol?

A

Increases osteoblast activity
Increases calcium reab in gut and kidney
Decreases phosphate excretion in kidney
Increases phosphate absorption in gut

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8
Q

What are the effects of PTH?

A

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

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9
Q

What does FGF23 do?

A

Blocks sodium phosphate co transporter in PCT like PTH, encouraging excretion of both in the urine
It also inhibits calcitriol

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10
Q

What is calcitriol inhibited by?

A

FGF23

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11
Q

How does hypocalcaemia present?

A
Cats go numb:
Convulsions
Arrythmias
Tetany
Paraesthesia
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12
Q

What are the 2 signs of hypocalcaemia?

A

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

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13
Q

What are the causes of hypocalcaemia?

A

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

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14
Q

How does hypercalcaemia present?

A

Stones- renal effects (kiney stones)
Abdominal moans- GI effects (anorexia, nausea, dyspepsia)
Psychic groans- CNS effects (fatigue, depression etc)

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15
Q

What are the causes of hypercalcaemia?

A

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

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16
Q

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

A

As calcium falls, PTH rises

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

17
Q

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

A

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

18
Q

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

A

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

19
Q

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

A

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

20
Q

How is primary hyperparathyroidism treated?

A

Parathyroidectomy/tumor removal

21
Q

How is secondary hyperparathyroidism treated?

A

Vitamin D supplements (25 hydroxy vitamin D)`

22
Q

How is tertiary hyperparathyroidism treated?

A

Parathyroidectomy

23
Q

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

A

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

24
Q

What is the difference between calcitonin and calcitriol?

A

Calcitriol is the active form of vitamin D

Calcitonin is a hormone that reduces levels of calcium

25
Q

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

A

Sunlight- this involves vitamin D3

Diet- this involves vitamin D2

26
Q

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

A

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

27
Q

What is the main difference between primary and secondary hyperparathyroidism?

A

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

28
Q

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

A

PTH

29
Q

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

A

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

30
Q

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

A

Primary hypercalcaemia due to pituitary adenoma

Tertiary hypercalcaemia due to chronic renal failure

31
Q

What is the diagnostic approach to vitamin D deficiency?

A

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

32
Q

What form of vitamin D is hard to measure?

A

Calcitriol