Calcium is an important mineral in our body which is mainly located in our bones. Besides being an important component of bone, calcium is also important for the proper functioning of muscles, nerve cells, blood clotting and transport of other minerals in our body. Calcium is present in dairy products, cheese, vegetables, nuts and legumes. The calcium balance is maintained by the absorption of calcium in the intestine and bone and the absorption and excretion of calcium in the kidneys. Factors affecting this balance are the acidity of the blood, the parathyroid hormone (PTH), vitamin D, and the magnesium concentration in the blood.

Signs and symptoms that may be due to low calcium levels in the blood are tingling, muscle contractions and arrhythmias. Signs and symptoms of excessive calcium in the blood are nausea, vomiting, constipation, excessive urination, muscle weakness and cardiac arrhythmias.

Determinining the cause
Tubular disorders are frequently accompanied by a disturbance in the absorption or excretion of calcium. Whether too much or too little calcium is excreted in the urine can be estimated by calculating the excretion of calcium by the kidney tubules from a urine portion. Furthermore, usually a 24-hour urine sample will be collected. Depending on the results of the initial studies, further diagnostic tools will be used to identicate the possible cause. Specific tests to investigate the function of the kidney tubules or genetic testing for suspected genetic / hereditary cause could be needed.

The treatment consists of removing the cause, if possible. If the cause is hereditary or the result of chronic damage to the renal tubules, this is not always possible.

–    Bartter syndrome
–    Gitelman syndrome