Clinical Calcium Homeostasis

Question 1

what are the dietry sources of calcium?

Answer 1

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

Question 2

what are the functions of calcium?

Answer 2

bone formation cell division and growth muscle contraction neurotransmitter release

Question 3

wat proportion of calcium is bound in plasma?

Answer 3

45% bound- mainly to albumin 10%non ionised 45% ionised

Question 4

what is the normal range of plasma calcium?

Answer 4

2.20-2.60 mmol/l

Question 5

how do we calculate free calcium?

Answer 5

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

Question 6

acidosis…. ionised calcium thus predisposing to …..

Answer 6

increases hypercalcaemia

Question 7

what are the soures of vitamin D?

Answer 7

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 

Question 8

an increase in calcium does what to PTH?

Answer 8

decreases

Question 9

a decrease in calcium does what to PTH?

Answer 9

increases

Question 10

how are alteratioins in ECF Ca levels transmitted into the parathyroid cells?

Answer 10

via calcium-sensing receptor (CaSR)

Question 11

when is PTH secreted in response to calcium

Answer 11

a fall in calcium

Question 12

true or false: PTH mediates the conversion of vitamin D from its inactive to active form

Answer 12

true

Question 13

what is hypocalcaemia?

Answer 13

serum calcium <2.20

Question 14

these are the clinical features of hypocalcaemia

Answer 14

Question 15

what are the causes of hypocalcaemia?

Answer 15

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

Question 16

what are the investigations of hypocalcaemia?

Answer 16

ECG

– Serum calcium – Albumin
– Phosphate
– PTH

– U&Es
– Vitamin D
– Magnesium

Question 17

this is the investigation of hypocalcaemia flow chart

Answer 17

Question 18

what does hypoparathyroidism result from

Answer 18

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)

Question 19

when does Pseudohypoparathyroidism present?

Answer 19

which presents in childhood, refers to a group of heterogeneous disorders defined by target organ (kidney and bone) unresponsiveness to PTH

Question 20

what are the characteristics of Pseudohypoparathyroidism

Answer 20

t is characterized by hypocalcemia, hyperphosphatemia and, in contrast to hypoparathyroidism, elevated rather than reduced PTH concentrations

Question 21

what is the treatment of hypocalcaemia?

Answer 21

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

Question 23

what are some vitamin D requirements?

Answer 23

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

Question 24

what are the causes of hypercalcaemia?

Answer 24

Question 25

what are the clinical features of hypercalcaemia

Answer 25

Question 26

how would you examen hypercalcaemia?

Answer 26

Lymph nodes

– Concerns about malignancy (breast, lung etc.)

Question 27

what are the investigations of hypercalcaemia?

Answer 27

U&Es

– Ca
– PO4
– Alk phos
– Myeloma screen – Serum ACE
– PTH

Question 28

what are the causes of primary hyperparathyroidism?

Answer 28

nephrolithiasis

bone disease

asymptomatic

Question 29

what are the investigations of primary hyperparathyroidism?

Answer 29

Ca, PTH
• U&Es: check renal function
• Abdominal imaging: renal calculi
• DEXA: osteoporosis
• 24 hour urine collection for calcium: Excl. FHH • Vitamin D

ultrasound

Question 30

what are the indications for surgery in primary hyperparathyroidism?

Answer 30

Question 31

what is the treatment for primary hyperparathyroidism?

Answer 31

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)

Question 32

what is familial hypocalciuric hypercalcaemia?

Answer 32

low levels of urinary calcium

Autosomal dominant disorder of the calcium sensing receptor

Benign, no therapy indicated

Question 33

what is the management of hypercalcaemia?

Answer 33

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

Question 34

what is the 2nd line management?

Answer 34

glucocorticoids

calcitonin

calcimimetics

parathyroidectomy