Clinical Calcium Homeostasis Flashcards
What are some dietary sources of calcium?
- Milk, cheese and other dairy foods
- Green leafy vegetables such as broccoli
- Soya beans
- Tofu
- Nuts
- Bread and anything made from fortified flour
- Fish where you eat the bones
What are some functions of calcium?
- Bone formation
- Cell division and growth
- Muscle contraction
- Neurotransmitter release
What percentage of calcium is found where?
98.9% in bones
1% in cells
0.1% in ECF
What are the proportions of plasma calcium concentrations?
- 45% bound (mainly to albumin)
- 10% non-ionised or complexed to citrate
- 45% ionised (biologically important)
What is the normal range of calcium?
2.2 - 2.6mmol/L
How is free calcium calculated?
- Increased albumin decreases free calcium
- Decreased albumin increases free calcium
- Adjust calcium by 0.01mmol/L for each 5g/L reduction in albumin from 40g/L
How does increased albumin impact free calcium levels?
Decreases free calcium
How does decreased albumin impact free calcium levels?
Increases free calcium
When working out free calcium, how is calcium adjusted for reduction in albumin?
Adjust calcium by 0.01mmol/L for each 5g/L reduction in albuymin from 40g/L
Does acidosis increase or decrease ionised calcium?
Increases
Since acidosis increases ionised calcium, what does it predispose?
Hypercalcaemia
If Mr Bloggs has calcium of 2.55mmol/L and his albumin is 30g/L, what is his corrected calcium?
What foods is vitamin D found in?
- Oily fish such as salmon
- Eggs
- Fortified fat spreads
- Fortified breakfast cereals
- Some powdered milks
What are some groups at risk of vitamin D deficiency?
- Pregnancy
- Children
- Elderly
What part of parathyroid glands respond directly to changes in calcium concentrations and secrete parathyroid hormone?
Chief cells
How are alterations in ECF calcium levels transmitted into parathyroid cells?
Via calcium-sensing receptor (CaSR)
How does increases serum calcium impact secretion of parathyroid hormone?
How does decreased serum calcium impact secretion of parathyroid hormone?
What are the effects of parathyroid hormone (PTH)?
- Direct effects that promotes reabsorption of calcium from renal tubules and bones
- Lengthy exposure to inappropriate levels of PTH can lead to osteoporosis
- Mediates the conversion of vitamin D from its inactive to active form
- This conversion takes place in the liver
What does PTH stand for?
Parathyroid hormone