Endo - Calcium dysregulation

Question 1

What cause an increased serum calcium?

Answer 1

• Vitamin D

- Parathyroid hormone

Question 2

What causes a decreased serum calcium?

Answer 2

Calcitonin

Question 3

How is vitamin D formed and metabolised?

Answer 3

Formed
- UVB light on the skin converts 7-dehyrocholesterol into pre-vitamin D3, then vitamin D3
Metabolised:
- Vitamin D3 goes to the liver when 25-hydroxylase coverts it into 25(OH)cholecalciferol
- Then 1 alpha-hydroxylase, in the kidney, converts it into 1,25(OH)cholecalciferol

Question 4

What is the effect of calcitriol?

Answer 4

Increases osteoblast activity

Increases calcium absorption at the gut and kidneys

Question 5

What is the effect of PTH?

Answer 5

Increases osteoblast activity
Increases calcium absorption at the gut and kidneys
Stimulates 1 alpha-hydroxylase which increases calcitriol levels
Inhibits sodium/phosphate co-transporter which reduces phosphate levels

Question 6

What are the symptoms of hypocalcaemia?

Answer 6

• Sensitises excitable tissue; muscle cramps, tetany, tingling
• Paraesthesia
• Convulsions
• Arrythmias

Question 7

What is Chvostek’s sign and Trosseau’s sign?

Answer 7

Chvostek’s - facial paraesthesia

Trosseau’s - carpopedal spasm

Question 8

What can cause hypocalcaemia?

Answer 8

Low PTH:

• Surgical - neck surgery
• Auto-immune
• Magnesium deficiency
• Congenital

Low vitamin D levels:
-Deficiency - diet, UV light, malabsorption, impaired production (renal failure)

Question 9

What are the symptoms of hypercalcaemia?

Answer 9

• Stones (renal effects)
• Abdominal moans (GI effects)
• Psychic groans (CNS effect)

Question 10

What are the causes of hypercalcaemia?

Answer 10

• Primary hyperparathyroidism:
  
  • Too much PTH
  • Usually due to parathyroid gland adenoma
  • No negative feedback: high PTH but high calcium
• Malignancy:
  
  • Bony metasteses
  • Certain cancers release PTH-related peptide
• Vitamin D excess (rare)

Question 11

What is the relationship between PTH and calcium?

Answer 11

When calcium levels fall, calcium sensor receptors detect this and increase PTH levels and inverse for high calcium levels

Question 12

What occurs in primary hyperparathyroidism?

Answer 12

A parathyroid adenoma in the thyroid gland causes an increased level of PTH, which increases calcium levels in the body, but has no negative feedback

Question 13

What is the treatment for hyperparathyroidism?

Answer 13

A parathyroidectomy

Question 14

What occurs in secondary hyperparathyroidism?

Answer 14

A normal physiological response to hypocalcaemia:
- Low calcium leads to high PTH
High PTH requirement leads to enlarged PT glands

Question 15

What causes secondary hyperparathyroidism?

Answer 15

A low vitamin D as it is needed for calcium reabsorption
OR
Renal function is impaired which leads to the lack of 1 alpha-hydroxylase, so calcitriol cannot be produced

Question 16

What is the treatment for secondary hyperparathyroidism?

Answer 16

Vitamin D replacement (normal renal function)
- Give 25 hydroxy vitamin D

In patients with renal failure give active vitamin D
- Alfacalcidol

Question 17

What is tertiary hyperparathyroidism?

Answer 17

• All of the renal glands have become hyperplastic
• Usually occurs through chronic renal failure
• This causes a chronic vitamin D deficiency
• The hyperthyroid glands grow as they try to produce more PTH

Question 18

What is the treatment for tertiary hyperparathyroidism?

Answer 18

Parathyroidectomy