Disorders of Calcium Metabolism

Question 1

What are the clinical manifestations of hypercalcaemia?

Answer 1

stones, bones, abdominal moans and psychic groans

Question 2

What is primary hyperparathyroidism?

Answer 2

autonomous inappropriate PTH overproduction leading to hypercalcaemia

Question 3

What is secondary hyperparathyroidism?

Answer 3

appropriate PTH increase in response to hypocalcaemia

Question 4

What is tertiary hyperparathyroidism?

Answer 4

Gland has become overactive after initial secondary hyperparathyroidism

Question 5

What are the main causes of primary hyperparathyroidism?

Answer 5

adenoma, hyperplasia, carcinoma (rare)

Question 6

How do we diagnose primary hyperparathyroidism?

Answer 6

high calcium and PTH
phosphate, bicarbonate low (excreted)
ALP normal (increased if severe)
imaging

Question 7

How do we treat primary hyperparathyroidism?

Answer 7

rehydration
adenomectomy or drugs
- bisphosphonates (inhibits osteoclasts, bone resorption)
- furosemide (inhibits distal calcium resorption)
- calcitonin (inhibits osteoclast)
- GC (inhibit vit D conversion to calcitriol)
- calcimimetics (bind calcium receptor - inhibit PTH release)

Question 8

What are the main reasons of malignant disease causing hypercalcaemia?

Answer 8

PTHrP released from solid tumours, or have 1-hydroxylase activity (synthesis calcitriol)

bone tumours stimulate osteoclast activation (cytokines) –> bone resorption

Question 9

How do we diagnose malignancy?

Answer 9

raised calcium
suppressed PTH
ALP very high

Question 10

What are the treatment principles of malignant hypercalcaemia?

Answer 10

rehydration
then drugs
treat underlying malignancy (srugery, chemotherapy)

Question 11

How does factitious hypercalcaemia occur?

Answer 11

raised calcium due to high plasma albumin

due to dehydration, venous stasis, or xs IV albumin

Question 12

how does sarcoidosis lead to hypercalcaemia?

Answer 12

hydroxylation of vitamin D in granulomas, leads to high calcium, low PTH
affects lungs mainly (ass. symptoms) and skin (ulcers, lumps, discolouration)

Question 13

What is the mechanism behind familial hypocalciuric hypercalcaemia (FHH)?

Answer 13

parathyroid calcium sensor less sensitive to calcium PTH suppression

Question 14

What are the clinical manifestations of hypocalcaemia?

Answer 14

increased neuromuscular excitability

mental change

Question 15

What are the two signs used to test for hypocalcaemia?

Answer 15

Chvostek’s sign: facial nerve in front of tragus tapped causing momentary muscle contraction in face

Trousseau’s sign: brachial artery occluded using BP cuff (3 min) causing neuromuscular irritability which induces spasm of hand and forearm muscles

Question 16

What are the causes/risk factors for vitamin D deficiency?

Answer 16

lack of sun, diet, malabsorption, chronic renal or liver disease, defective enzymes in vitamin D metaobolic pathway, tanned/dark skinned

Question 17

What are the clinical features of vitamin D deficiency?

Answer 17

low calcium, high PTH

osteomalacia - bones soft, pain, fractures, defective mineralisation/calcification

Question 18

What are the causes of vitamin D deficiency?

Answer 18

Rickets
Inherited causes 
- deficient 1-ydroxylase
- defective calcitriol receptor
- hypophosphataemic Rickets (mutation, excessive urine loss)
- hypophosphatasia (low ALP)

Question 19

What are the causes of hypoparathyroidism?

Answer 19

acquired - surgery, suppresed secretion

inherited - developmental parathyroid problems, genetic disorders

Question 20

What are the biochemical features of hypoparathyroidism?

Answer 20

low calcium, low PTH (inappropriate), phosphate high

Question 21

What are treatments for hypocalcaemia?

Answer 21

acute - IV calcium
oral calcium, vitamin D intramuscular injection if malabsorption present, sometimes magnesium

close monitoring of plasma [calcium] necessary

Question 22

What is factitiuous hypocalcaemia?

Answer 22

Due to low plasma albumin caused by malnutrition/malabsorption/liver disease (reduced synthesis)

Question 23

What is osteoporosis?

Answer 23

reduced bone mineral density leading to increased risk of fracture
often age associated

Question 24

What is the MAIN difference between osteoporosis and osteomalacia?

Answer 24

osteoporosis DOESN’T AFFECT routine biochemistry or histology

osteomalacia has abnormal biochemistry, histology