Pathological disturbances calcium metabolism

Question 1

What can cause a transient hypercalcaemia?

Answer 1

non-fasting, after a meal high in calcium

Question 2

What can cause a falsely raise hypercalcaemia?

Answer 2

extended tourniquet application

Question 3

Name three most common causes of hypercalcaemia?

Answer 3

• Primary hyperparathyroidism
• Malignancy-related hypercalcaemia
• Vitamin D excess

Question 4

Standard investigation for hypercalcaemia?

Answer 4

Total calcium (calculated ionised Ca)
PTH
Phosphate
Vitamin D (25 hydroxyvitamin D)

Question 5

What can PTH at the upper range of normal, high calcium and low phosphate indicate?

Answer 5

Primary hyperparathyroidism

Question 6

What should be measured to calculate ionised calcium?

Answer 6

Anion gap – [(Na+K)-(Cl+HCO3)]
Albumin
Globulin

Question 7

Define primary hyperparathyroidism

Answer 7

Dysfunction of parathyroid gland with uncontrolled
secretion of PTH
- Adenoma
- Malignancy

Question 8

How does primary hyperparathyroidism cause hypercalcaemia?

Answer 8

Causes hypercalcaemia due to:

• increase bone resorption
• increase tubular reabsorption of Ca++
• increase 1,25 vitamin D activation

Question 9

what are:
- Renal stones
- Depressed CNS
- Neuromuscular weakness
- Clubbing of fingers and toes
symptomatic of?

Answer 9

primary hyperparathyroidism

Question 10

How can lymphoma lead to hypercalcaemia?

Answer 10

Ectopic production of 1,25 dihydroxyvitamin D by immune cells which under normal physiological conditions in negligible

Question 11

Name three mechanisms by which malignancy can lead to hypercalcaemia?

Answer 11

Ectopic production of 1,25 Vitamin D by lymphoma
Malignancies producing PTH related peptide
Lytic bone metastases

Question 12

PTH-related peptide producing cancers that can cause hypercalcaemia include?

Answer 12

• lung
• oesophagus
• head and neck
• renal cell
• breast
• ovary
• bladder

Question 13

Lytic bone metastases that can cause hypercalcaemia due to excess bone brake down include?

Answer 13

• multiple myeloma
• haematologic malignancies
• breast carcinoma

Question 14

Define secondary hyperparathyroidism.

Answer 14

Elevated PTH in response to prolonged hypocalcaemia.

Question 15

Most common cause of secondary hyperparathyroidism?

Answer 15

•Most commonly due to renal failure
- Reduced CYP27B1 activity (↓ serum 1,25D)
- unable to conserve Ca++
•Leads to ↑ bone resorption (renal osteodystrophy)

Question 16

What can the result of surgery for:
- Hyperparathyroidism
- Hyperthyroidism
- Malignancy of the neck
all cause?

Answer 16

hypoparathyroidism

Question 17

Symptoms of hypoparathyrodism?

Answer 17

• decrease neural excitation threshold
• repetitive response to single stimulus
• continuous activity may lead to: tetany (peripheral) and convulsions (central)

Question 18

What is sarcoidosis?

Answer 18

Granulomas disease (commonly lungs).  Leads to an accumulation of macrophages.  
Macrophages have high endogenous activity of CYP27B1 activity leading to unregulated 1,25D production.  Eventually spills over into the circulation to cause hypercalcaemia and PTH suppression

Question 19

Define pseudohypoparathyroidism

Answer 19

A group of disorders caused by PTH receptor defects (at least 5 variants)

Question 20

How does pseudohypoparathyroidism present on biochemistry results?

Answer 20

Decreased calcium levels

Grossly elevated PTH