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?
what are the clinical features of hypercalcaemia
how would you examen hypercalcaemia?
Lymph nodes
– Concerns about malignancy (breast, lung etc.)
what are the investigations of hypercalcaemia?
U&Es
– Ca
– PO4
– Alk phos
– Myeloma screen – Serum ACE
– PTH
what are the causes of primary hyperparathyroidism?
nephrolithiasis
bone disease
asymptomatic
what are the investigations of primary hyperparathyroidism?
Ca, PTH
• U&Es: check renal function
• Abdominal imaging: renal calculi
• DEXA: osteoporosis
• 24 hour urine collection for calcium: Excl. FHH • Vitamin D
ultrasound
what are the indications for surgery in primary hyperparathyroidism?
what is the treatment for primary hyperparathyroidism?
Medical management
– Generous fluid intake
– Cinacalcet (acts as a calcimetic, i.e. mimics the effect of calcium on the calcium sensing receptor on Chief cells, this leads to a fall in PTH and subsequently calcium levels)
what is familial hypocalciuric hypercalcaemia?
low levels of urinary calcium
Autosomal dominant disorder of the calcium sensing receptor
Benign, no therapy indicated
what is the management of hypercalcaemia?
Rehydration
– 0.9% Saline 4-6 litres
over 24 hours
– Monitor for fluid overload
– Consider dialysis if severe renal failure
Afterrehydration, intravenous bisphosphonates
– Zolendronic acid 4mg over 15 mins
– Give more slowly and consider dose reduction if renal impairment
– Calcium will reach nadir at 2-4 days
what is the 2nd line management?
glucocorticoids
calcitonin
calcimimetics
parathyroidectomy
