Hyper and Hypocalcaemia Flashcards
1
Q
Dietary intake of calcium
A
- Dietary intake- 25mmol/day (1g for adults)
2
Q
Normal calcium levels
A
2.12-2.65 mmol/L
3
Q
Biological functions of calcium
A
- muscle contraction
- nerve excitability
- intracellular messanging
- blood coagulation
- enzymes of intermediary metabolism
4
Q
How is calcium found in the serum
A
- Free (unbound/ionised)- 47%
- BOUND to albumin -47%
- Complexed -6%
Feedback mechanisms are regulated by the FREE fraction
FREE fraction is physiologically important
5
Q
How to measure calcium levels
A
Lab measures either
- FREE calcium or (physiologically important part)
- Total (bound + free) calcium
Adjusting the calcium
- measure total calcium
- “what if the serum total calcium would have ben if the albumin had been normal
Ca (adj) = Ca (tot) + [0.02(45-ab)}
6
Q
Which three hormones regulate calcium levels in the blood and tissues?
A
- PTH from parathyroid gland
- vitamin D (cholecalciferol) from the diet and skin
- Calcitonin from the thyroid gland
7
Q
Parathyroid homrone (PTH) properties
A
- 84 amino acid polypeptidde produced by the Parathyroid glands
- secretion is regulated by free calcium , sensed by calcium sensing receptors
- on parathyroid cells - minute-minute responses to ionised Ca
- main physiological ligan is calcium
- serve as calciostat for calcium homeostasis
- as calcium levels rise, PTH falls; as calcium levels fall, OTH rises
8
Q
Calcium sensing receptor
A
- G coupled protein receptor
- Parathyroid cells - mediates effect of EC ionised Ca on OTH release
- Renal tubule - mediates effect of high peritubular ionised Ca to inhibit Ca reabsorption
9
Q
Calcium homeostasis: Low calcium
A
Actions are:
- increase osteoclast activity releasing ca2+ and PO4- from bones
- increase Ca2+ and decrease PO43- reabsorption from the kidney
- increases renal production of 1,25-dihydroxy-vitamin D3
10
Q
Calcium homeostasis: High calcium levels
A
