calcium

Question 1

what is the function of osteoclasts?

Answer 1

for bone reabsorption
release calcium and phosphate out of the bone

Question 2

what do osteoclasts express to increase activity?

Answer 2

RANK ligaments receptors

Question 3

what do osteoblasts do?

Answer 3

bone formation/ ossifications

Question 4

what controls bone remodelling?

Answer 4

oestrogen, PTH, glucocorticoids, IGH-1, growth hormone and insulin

Question 5

how does oestrogen effect bone remodelling?

Answer 5

inhibits osetoblastic cytokine stimulators
lack of oestrogen - leads to osteoporosis

Question 6

what does PTH do in relation to bone remodelling?

Answer 6

enhances bone turnover

Question 7

what does VItD do in relation to bone remodelling?

Answer 7

enhances osetoblast activity

Question 8

hwo do glucocorticoids effect bone remodelling?

Answer 8

: initially inhibit osteoclast activity
- Prolonged use can cause osteoblast inhibition  osteoporosis

Question 9

what does IGH-1 do in relagtion to bone remodelling?

Answer 9

: initially inhibit osteoclast activity
- Prolonged use can cause osteoblast inhibition  osteoporosis

Question 10

can untreated diabetes effects bones?

Answer 10

insulin enhances bone formation
untreated diabetes can lead to osetoporosis

Question 11

what are the functions of calcium?

Answer 11

• Coagulation
• 2nd messenger – cell signalling
• Nerve function
• Muscular contraction
• Cardiac action potential

Question 12

where is calcium found?

Answer 12

• 99% found in bone – 1% is either unbound or bound to albumin

Question 13

what are normal calcium values?

Answer 13

• 2.2-2.6nmol/L

Question 14

how does PTH affect calcium?

Answer 14

increase serum calcium

Question 15

how does calcitonin affect calcium?

Answer 15

reduces serum calcium

Question 16

what is unbound calcium affected by?

Answer 16

plasma protein - albumin
and pH

Question 17

what happens to calcium in alkalotic conditions?

Answer 17

more Ca bound to albumin eg anxiety attack causing resp alkalosis

Question 18

what happens to calcium in acidotic conditions?

Answer 18

more free Ca in blood eg hypercapnic

Question 19

what stimulates PTH secretion?

Answer 19

low serum calcium
increased serum phosphate

Question 20

what inhibits secretion of PTH?

Answer 20

raised serum calcium or calcitriol (activated VitD)

Question 21

what are the effects on bones, intestines and kidneys of PTH?

Answer 21

• Bone: enhances osteoblast and clast  more bone reabsorption and Ca/ phosphate release
• Intestine: increases Ca absorption via 1,25 dihydroxy vitD
• Kidneys: increases Ca reabsorption, inhibits phosphate reabsorption, activates 1,25 hydroxy VitD

Question 22

where does vitD come from?

Answer 22

UV and skin

Question 23

where is vitD metabolised to be activated?

Answer 23

• Metabolised by liver and proximal tubular cells in kidneys to be activated

Question 24

what are the effects of VItD in bone, gut and kidneys?

Answer 24

• Bone: increases osteoblast activity  strengthens bone
• Gut: enhances calcium and phosphate absorption
• Gut and kidney: increase serum ca and phosphate for bone mineralisation

Question 25

where is calcitonin secreted from?

Answer 25

secreted from C cells of thyroid by increased Ca levels

Question 26

what is the aetiology of hypercalcaemia?

Answer 26

• Excessive PTH: primary hyperparathyroidism, tertiary hyperparathyroidism, ectopic PTH secretion
• Malignancy: myeloma, bony mets, paraneoplastic syndromes eg parathyroid adenomas
• Excess vitD: exogenous excess/ granulomatous disease eg sarcoidosis
• Renal: severe AKI
• Drugs: thiazide like diuretics/ lithium
• Hereditary: familial hypocalciuric hypercalcaemia

Question 27

what are the symptoms of hypercalcaemia?

Answer 27

BONES, STONES, GROANS, MOANS and THRONES
- Bones: bone pain and pathological fracture (not caused by trauma)
- Renal stones: calculi  renal colic
- Abdo groan: abdo pain, vomiting, pancreatitis
- Psychic moans: confusion, hallucinations, lethargy, depression
- Thrones: constipation

Question 28

what would you do with >3nmol/L calcium levels?

Answer 28

• > 3nmol/L want to urgently admit  normal saline IV – 4L/24hrs
• Hypercalcemia refractory to rehydration may require bisphosphonates (promote osteoblasts)

Question 29

what is defined as hypocalcaemia?

Answer 29

<2.2mmol/L

Question 30

what is the aetiology of hypocalcaemia?

Answer 30

• PTH deficiency: primary hypoparathyroidism (autoimmune), parathyroid damage (post thyroid/ parathyroid surgery or post neck irradiation), hypomagnesium
• vitD deficiency/ osteomalacia
• acute pancreatitis
• CKD
• drugs: bisphosphonates, calcitonin

Question 31

what symptoms are seen with hypocalcaemia?

Answer 31

• muscle weakness/ cramps
• muscle tetany/ spasm
• perioral paraesthesia
• psychological disturbances
• seizures

Question 32

what is trousseaus sign indicating hypocalcaemia?

Answer 32

occlusion of brachial artery eg with blood pressure cuff cuff and leads to involuntary contraction of hand/ wrist

Question 33

what is chvosteks sign indicating hypocalcaemia?

Answer 33

tapping over facial nerve causes contraction of facial nerve  mouth moves towards site of tapping

Question 34

what ECG changes can be seen in hypocalcaemia?

Answer 34

ECG may show OT prolongation - torsades de pointes and cardiac arrest

Question 35

what is the management of hypocalcaemia?

Answer 35

• replacing calcium while investigating and finding initial cause
• eg oral calcium
• severe or ECG changes present  calcium gluconate