Clinical Calcium Homeostasis Flashcards
what are the dietry sources of calcium?
milk, cheese and other dairy foods • green leafy vegetables – such as broccoli, cabbage and okra, but not spinach • soya beans • Tofu • nuts • bread and anything made with fortified flour • fish where you eat the bones – such as sardines and pilchards
what are the functions of calcium?
bone formation cell division and growth muscle contraction neurotransmitter release
wat proportion of calcium is bound in plasma?
45% bound- mainly to albumin 10%non ionised 45% ionised
what is the normal range of plasma calcium?
2.20-2.60 mmol/l
how do we calculate free calcium?
increased albumin decreases free calcium – Decreased albumin increases free calcium – Adjust Ca2+ by 0.1mmol/l for each 5g/l reduction in albumin from 40g/l
acidosis…. ionised calcium thus predisposing to …..
increases hypercalcaemia
what are the soures of vitamin D?
vitamin D is also found in a small number of foods. Good food sources are: • oily fish – such as salmon, sardines and mackerel • eggs • fortified fat spreads • fortified breakfast cereals • some powdered milks 
an increase in calcium does what to PTH?
decreases
a decrease in calcium does what to PTH?
increases
how are alteratioins in ECF Ca levels transmitted into the parathyroid cells?
via calcium-sensing receptor (CaSR)
when is PTH secreted in response to calcium
a fall in calcium
true or false: PTH mediates the conversion of vitamin D from its inactive to active form
true
what is hypocalcaemia?
serum calcium <2.20
these are the clinical features of hypocalcaemia
what are the causes of hypocalcaemia?
Disruption of parathyroid gland due to total thyroidectomy. May be temporary or permanent
Followingselectiveparathyroidectomy(usually transient & mild)
Severe vitamin D deficiency
Mg2+ deficiency (which drug can cause this?)
Cytotoxicdrug-inducedhypocalcaemia
Pancreatitis, rhabdomyolysis and large volume blood tranfusions
what are the investigations of hypocalcaemia?
ECG
– Serum calcium – Albumin
– Phosphate
– PTH
– U&Es
– Vitamin D
– Magnesium
this is the investigation of hypocalcaemia flow chart
what does hypoparathyroidism result from
agenesis (e.g. DiGeorge syndrome)
– destruction (neck surgery, autoimmune disease)
– Infiltration (e.g. haemochromatosis or Wilson’s disease)
– reduced secretion of PTH (neonatal hypocalcaemia, hypomagnesaemia)
– Resistance to PTH (discussed on next slide)
when does Pseudohypoparathyroidism present?
which presents in childhood, refers to a group of heterogeneous disorders defined by target organ (kidney and bone) unresponsiveness to PTH
what are the characteristics of Pseudohypoparathyroidism
t is characterized by hypocalcemia, hyperphosphatemia and, in contrast to hypoparathyroidism, elevated rather than reduced PTH concentrations
what is the treatment of hypocalcaemia?
Commence oral calcium tablets
• If post thyroidectomy repeat calcium 24 hours
later
- If vit D deficient, start vitamin D
- If low Mg2+, stop any precipitating drug and replace Mg2+
“Severe” hypocalcaemia (Symptomatic or <1.9mmol/L)
This is a medical emergency
Administer IV calcium gluconate
Initial bolus (10-20ml 10% calcium gluconate in 50-100ml of 5% dextrose IV over 10 minutes with ECG monitoring)
Calcium gluconate infusion
Treat the underlying cause
what are some vitamin D requirements?
Vitamin D requires hydroxylation by the kidney to its active form, therefore the hydroxylated derivatives alfacalcidol or calcitriol should be prescribed if patients with severe renal impairment require vitamin D therapy
what are the causes of hypercalcaemia?
