Disorders of Calcium, magnesium and phosphate Flashcards
What blood test tube should never be used for or before serum calcium?
EDTA - it gets rid of the calcium
What are the 4 main roles of calcium physiologically?
1) Muscle contraction
2) Neuronal excitation
3) Enzyme activity (Na/K ATPase, hexokinase)
4) Blood clotting
What is the structural role of calcium in the body?
Key component of hydroxyapatite which is the predominant mineral in bone
What kind of chemical is phosphate?
Monovalent anion PO4-
What are the 3 physiological roles of phosphate?
1) The P in ATP
2) Intracellular signalling
3) Cellular metabolic processes eg. glycolysis
What are the 3 structural roles of phosphate in the body?
1) Backbone of DNA
2) Component of hydroxyapatite - predominant mineral in bone
3) Membrane phospholipids
Is phosphate predominantly extracellular or intracellular?
Intracellular
What kind of ion is magnesium?
Divalent cation
What are the 4 physiological roles of magnesium?
1) Cofactor of ATP - our fuel
2) Neuromuscular excitability
3) Enzymatic function
4) Regulates ion channels
What is the structural role of magnesium?
Comprises 0.5-1% of bone
Is magnesium an intracellular or extracellular ion?
Predominantly intracellular
If you receive serum calcium serum results which are very unusual what is the likely problem?
EDTA contamination
In terms of homeostasis, when something goes wrong one of what 4 things is normally the cause of the abnormality?
1) Intake
2) Tissue redistribution
3) Storage
4) Excretion/loss
What is the normal range of calcium?
2.20-2.60mmol/L
What are the 2 key controlling factors in regulating calcium?
1) PTH
2) Vit D and metabolites
What 3 organs have a role in calcium levels?
1) GI uptake
2) Renal clearance
3) Bone
What 3 types of calcium make up total calcium?
Total Ca = Ionised Ca + Bound Ca + Complexed Ca
What is the physiologically active fraction of total calcium?
Ionised calcium
What are the 3 roles of ionised calcium?
1) Acts on calcium sensing receptor
2) Regulates PTH
3) Cellular effects
Which is the main binding protein for bound calcium?
Albumin
Is bound calcium physiologically active?
No
In what 2 forms is complexed calcium found?
1) Calcium phosphate
2) Calcium citrate
What is meant by adjusted calcium?
Calcium values which are corrected for changes in albumin:
Adjusted Ca = Total Ca + (40-Alb) x 0.025
Are the reference values for adjusted calcium different to those for total calcium?
No