calcium Flashcards
what is the function of osteoclasts?
for bone reabsorption
release calcium and phosphate out of the bone
what do osteoclasts express to increase activity?
RANK ligaments receptors
what do osteoblasts do?
bone formation/ ossifications
what controls bone remodelling?
oestrogen, PTH, glucocorticoids, IGH-1, growth hormone and insulin
how does oestrogen effect bone remodelling?
inhibits osetoblastic cytokine stimulators
lack of oestrogen - leads to osteoporosis
what does PTH do in relation to bone remodelling?
enhances bone turnover
what does VItD do in relation to bone remodelling?
enhances osetoblast activity
hwo do glucocorticoids effect bone remodelling?
: initially inhibit osteoclast activity
- Prolonged use can cause osteoblast inhibition osteoporosis
what does IGH-1 do in relagtion to bone remodelling?
: initially inhibit osteoclast activity
- Prolonged use can cause osteoblast inhibition osteoporosis
can untreated diabetes effects bones?
insulin enhances bone formation
untreated diabetes can lead to osetoporosis
what are the functions of calcium?
- Coagulation
- 2nd messenger – cell signalling
- Nerve function
- Muscular contraction
- Cardiac action potential
where is calcium found?
- 99% found in bone – 1% is either unbound or bound to albumin
what are normal calcium values?
- 2.2-2.6nmol/L
how does PTH affect calcium?
increase serum calcium
how does calcitonin affect calcium?
reduces serum calcium
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
