calcium

TOTAL CALCIUM

Calcium is the most abundant mineral in the body, there being 1 kg (25000 mmol) calcium in the body of which 99% is present in bone. The remaining 1% circulates in blood in two main forms, the albumin bound fraction which accounts for 50% of the total calcium and it is physiologically inactive.

The other part is the free ionized calcium which is physiologically active. The free ionized calcium is essential for coagulation process,
neuromuscular activity, membrane permeability, and the activity of many
enzymes. Ionized calcium is also very important inside the cell where it acts as a second messenger for many hormones.

There are many factors that control the level of circulating free ionized calcium which include:-
1- Parathyroid hormone.
2- 1,25 dihyroxy cholecalciferol, 1,25 DHCC (calcitriol).
3- Calcitonin.
In the lab, we measure the total calcium (free + bound).

Biochemical Bone Profile BBP

It includes
1- Serum Calcium
2- Serum phosphate
3- Serum albumin
4- Alkaline phosphatase activity


Clinical significance
Normal range – 2.10 – 2.60 mmol/L (8.5-10.5 mg/dl).
Serum total calcium increases in hyperparathyroidism, malignancy with metastases, multiple myeloma and vitamin D intoxication. Serum total calcium may be increased as an artifact due to excessive venous stasis during blood collection and therefore correction for albumin or total protein has to be made.
Serum total calcium decreases in hypoparathyroidism, osteomalacia, rickets, chronic renal failure, malabsorption syndrome and hypoproteinemia.

Determination of Calcium

(Kit method)
Principle
Colorimetric determination of Ca, without deproteinization using Ocresolphthalein
complexone, interference due to Mg+2 ion is eliminated by 8 hydroxyquinoline.