Calcium and Phosphate Metabolism and Homeostasis Flashcards
How is calcium distributed in the body?
- 99% of total Ca is in bones
- Rest is intracellular and in extracellular fluid (eg. blood)
What is the total calcium in the body?
Around 25000 mmol
What are the biological roles of calcium?
- Muscle contraction
- Nerve excitation
- Blood coagulation
- Intracellular messenger
- Enzymes of intermediary metabolism
How is calcium distributed in the blood ?
- Around 47% free (ionised/bound)
- Around 47% bound to albumin
- Around 6% complexed
In blood what calcium distribution area is important physiologically and why?
-Free calcium is important as it regulates feedback mechanisms
What are the main organs involved in calcium homeostasis?
- Kidney
- Gut
- Bone
- Parathyroid glands
What are the main homones involved in metabolic control of calcium?
- PTH
- 1.25 DHCC/ calcitriol/ active vit D
What is our dietary intake of Ca and how much of this is absorbed and where?
- Around 25mmol/day
- Around 6mmol/day absorbed
- In duodenum and jejenum mainly
How much Ca does our kidneys filter and reabsorb and how much is lost in urine?
- Filters around 240mmol/day
- Around 234mmol/day reabsorbed.
- Urine around 6mmol/day
How much Ca does the skeleton release and how?
- Around 8 mmol/day, a similar amount is also laid back down in bone
- Through resorption
Which of the major hormones control absorption of Ca?
-1.25 DHCC
Which of the major hormones control reabsorption of Ca?
-PTH
Which of the major hormones control ressorption of Ca?
- 1.25 DHCC
- PTH
What measurements can we take for calcium in blood?
We can either measure free calcium of total calcium (bound and free).
If a patient has low albumin Ca conc then what implication does this have on results?
Total Ca will also be low but free Ca may still appear quite normal
If albumin conc is low can we still calculate what serum total would have been if it was normal and if so how?
- Yes
- Ca (adj) = Ca (tot) + [0.02(45-alb)]
What is normal serum calcium usually and what do values above and below this indicate?
- 2.2 - 2.6 mmol/L
- Below is hypocalcaemia
- Above is hypercalcaemia