Hypercalcaemia and Hypocalcaemia Flashcards
Where is most calcium in the body found?
Extracellularly
What three major mechanisms control calcium levels?
PTH - Vit D - Calcitonin
How does PTH act to control calcium levels?
Increases Ca levels - Acts on kidneys, GI tract and bone
What other side effect which is measurable by biochemistry does increased PTH cause?
Phosphate secretion in kidneys
What is the biologically active metabolite of Vit D?
1,25 dihydroxycholecalciferol OR calcitriol
How does Vit D act to control calcium levels?
Converted in the kidneys to calcitriol - Calcitriol acts on GI to increase absorption of calcium, acts on renal to increase calcium reabsorption and bone to mobilise calcium and phosphorus
How does Calcitonin act to control calcium levels?
Response to hypercalcaemia - Excreted by C cells of thyroid - Minimal physiological effects
What is involved in the total serum calcium measurement?
Calcium bound to albumin (35%) - Free Calcium (10%) - Ionised calcium (55%)
What type of calcium is physiologically significant?
Ionised calcium
When evaluating total calcium levels, what else is important to look at? Why?
Serum albumin - Whether physiologically important calcium abnormality may be present
Why is it important to follow up any hypercalcaemia finding?
Significant increases in ionised calcium can be associated with small increases in total calcium
What renal effects does hypercalcaemia have?
Interferes with descending Loop of Henle decreasing water reabsorption - Reduced ADH sensitivity - Reduced GFR causing azotaemia - Nephrocalcinosis (if phosphate also high)
