CALCIUM AND PHOSPHATE OVERVIEW AND FUNCTIONS
• Calcium and phosphorus are key minerals present in the bone, blood and soft tissue of the body and have several important functions. Phosphorus levels can influence calcium levels in the body, and vice versa.

• Calcium in the body is present in three major pools namely intracellularly in the free or ionized form, in the blood plasma bound to proteins as well as in the free form. However, the major amount of calcium is found in the bone in the mineralized form (99%) but 1% is available for rapid exchange with plasma calcium whenever needed.

• Calcium is critical for muscle contraction, maintaining healthy and strong bones and teeth, blood clotting, conducting nerve impulses, activation of the ovum, regulating heart beat and fluid balance within cells.

• Like calcium, major portion of body phosphate (approximately 85%) is present as mineralized bone. The rest of body phosphate is present in a variety of inorganic and organic compounds distributed across both intracellular and extracellular compartments.

• Phosphorus works closely with calcium to build and repair bones and teeth, help normal nerve function, and muscles contraction.

• Phosphates are also an important component of adenosine triphosphate (ATP) the high energy molecule necessary for several important cellular activities. They also form part of the structure of cell membranes, as well as important structural component of DNA and RNA.

• Any fluctuations in calcium and phosphate levels can therefore impact the normal function of muscles and nerves as well as affect bone health. The concentrations of these ions must therefore be maintained optimally to ensure there is no disease

• The organs involved in maintaining optimal levels of calcium and phosphate include intestines bone, and kidneys. The hormones involved in maintaining calcium and phosphorus are parathyroid hormone (PTH) vitamin D and calcitonin.

ROLE OF VITAMIN D AND PTH
• Vitamin D is needed to absorb calcium and phosphate from the diet. Even if you eat foods that are rich in calcium and phosphate, they won’t be absorbed into the body unless vitamin D is present in sufficient amounts

• For example if levels of calcium and phosphorus in blood are low, it is sensed by the parathyroid hormone (PTH) which in turn signals to the kidney to produce more vitamin D to increase their absorption from the intestine. At the same time, it signals to the bone to release more calcium and phosphorus from its reserve into the blood to maintain optimal levels

ROLE OF CALCITONIN
Calcitonin is another hormone that functions to reduce blood calcium levels. It is secreted when there is increased calcium levels (hypercalcemia) and has at least two main effects
• It enhances excretion of calcium via kidneys into urine
• Inhibition of calcium resorption from bone, which would reduce fluxes of calcium from bone into blood.

CALCIUM AND PHOSPHATE AND BONE HEALTH
Bone health is maintained by the action of local factors and hormones. These hormones can be divided into hormones that affect calcium and phosphate homeostasis and other hormones

In the human body parathormone, calcitriol (active vitamin D) and calcitonin are major players in the regulation of calcium and phosphate content.

PTH increases calcium and phosphate resorption from bone. On the other hand vitamin D increases absorption of calcium and vitamin D from the small intestine and ensures availability of these minerals for bone formation. Calcitonin reduces calcium resorption from bone and favours deposition

ROLE OF KIDNEYS IN CALCIUM AND PHOSPHATE METABOLISM
Normally functioning kidneys will remove excess phosphorus and calcium in the blood.
However, in kidney disease, the body is unable to get rid of extra phosphorus and phosphate builds up in your body and binds to calcium, which, in turn reduces calcium levels. When calcium levels become too low, PTH is secreted by the parathyroid glands in the neck which draws out extra calcium the body needs from the bones making them weak and prone to break.

CLINICAL CONDITIONS AND SYMPTOMS OF CALCIUM AND PHOSPHATE DEFICIENCY AND EXCESS
• Hypocalcaemia (decreased serum calcium) can be caused by vitamin D deficiency, PTH deficiency, kidneys or pancreatic disease. It may be asymptomatic; in severe cases there may be muscle cramps, confusion and tingling in the lips and fingers.

• Hypercalcaemia (excess serum calcium) is most often caused by PTH excess or from cancer. Symptoms of hypercalcaemia can be mild to severe. They may include increased thirst and urination, muscle weakness, stomach pain, nausea, bone pain, confusion and tiredness.

• Hyperphosphatemia (excess phosphate in blood) is mostly caused by kidney disease. Most people remain asymptomatic while others develop calcium deposits in the soft tissue. Often there is associated low calcium levels which can result in muscle spasms.

DIAGNOSIS
In kidney disease for example calcium and phosphate levels are disrupted and it is essential to regularly measure and monitor blood levels of calcium and phosphate. Normal calcium level in blood is between 8.5 to 10.5 mg/dl (4.3 to 5.3 mEq/L or 2.2 to 2.7 mmol/L). Phosphate level ranges between 2.5 to 4.5 mg/dL.

TREATMENT OF CALCIUM AND PHOSPHATE IMBALANCE
• Treatment of underlying disorder eg vitamin deficiency, kidney disease or parathyroid disease
• Supplementation of calcium and vitamin D as appropriate
• Restriction of phosphate and phosphate binders to bind excess phosphate in chronic kidney disease
• Parathyroid surgery to remove source excess of PTH when present

DIETARY SOURCES OF CALCIUM AND PHOSPHATE
• Dietary sources of calcium include dairy products, soya, vegetables such as broccoli, bok choy, kale and beans such as pinto and red. The RDA for calcium is 1,000 mg for most adults, though it may be higher in some adolescents
• Sources of phosphorus include dairy products, nuts, meat, beans and foods that contain phosphorus
additives such as colas and convenience foods. The recommended dietary allowance of phosphorus is 700 mg daily