calcium Flashcards by Emily Nicholson

what is the function of osteoclasts?

for bone reabsorption
release calcium and phosphate out of the bone

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what do osteoclasts express to increase activity?

RANK ligaments receptors

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what do osteoblasts do?

bone formation/ ossifications

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what controls bone remodelling?

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

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how does oestrogen effect bone remodelling?

inhibits osetoblastic cytokine stimulators
lack of oestrogen - leads to osteoporosis

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what does PTH do in relation to bone remodelling?

enhances bone turnover

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what does VItD do in relation to bone remodelling?

enhances osetoblast activity

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hwo do glucocorticoids effect bone remodelling?

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

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

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

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can untreated diabetes effects bones?

insulin enhances bone formation
untreated diabetes can lead to osetoporosis

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what are the functions of calcium?

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

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where is calcium found?

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

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what are normal calcium values?

2.2-2.6nmol/L

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how does PTH affect calcium?

increase serum calcium

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how does calcitonin affect calcium?

reduces serum calcium

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what is unbound calcium affected by?

plasma protein - albumin
and pH

what happens to calcium in alkalotic conditions?

more Ca bound to albumin eg anxiety attack causing resp alkalosis

what happens to calcium in acidotic conditions?

more free Ca in blood eg hypercapnic

what stimulates PTH secretion?

low serum calcium
increased serum phosphate

what inhibits secretion of PTH?

raised serum calcium or calcitriol (activated VitD)

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

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

where does vitD come from?

UV and skin

where is vitD metabolised to be activated?

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

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

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

where is calcitonin secreted from?

secreted from C cells of thyroid by increased Ca levels

what is the aetiology of hypercalcaemia?

- 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

what are the symptoms of hypercalcaemia?

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

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

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

what is defined as hypocalcaemia?

<2.2mmol/L

what is the aetiology of hypocalcaemia?

- 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

what symptoms are seen with hypocalcaemia?

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

what is trousseaus sign indicating hypocalcaemia?

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

what is chvosteks sign indicating hypocalcaemia?

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

what ECG changes can be seen in hypocalcaemia?

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

what is the management of hypocalcaemia?

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