Calcium

BT_PO 1.88 Outline the regulation of plasma calcium including the actions and control of vitamin D, parathyroid hormone and calcitonin

T / F  of the total calcium in plasma, 20% is present in the free ionised form

T / F  a decrease in plasma calcium causes the release of parathyroid hormone

T / F  PTH acts by directly (i) releasing calcium from bone, (ii) increasing calcium absorption from the GIT, and (iii) decreasing renal calcium excretion

T / F  vitamin D is converted to 1,25-dihydroxy cholecalciferol by UV light, which then acts to increase calcium absorption from the GIT

T / F  hypocalcaemia can prolong the QT interval

T / F  10 mL of 10% calcium chloride contains 6.8 mmol Ca++, and 10 mL of 10% calcium gluconate contains 2.2 mmol Ca++

Extra discussion questions:

  1. Following a total thyroidectomy, patients can develop hypocalcaemia. Can you explain why? What symptoms would develop, and what physiology explains these?
  2. Patients with bony metastases can develop hypercalcaemia. What is the mechanism of this? What symptoms would develop, and what physiology explains these?

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