<P> Hypocalcaemia, also spelled hypocalcemia, is low calcium levels in the blood serum . The normal range is 2.1--2.6 mmol / L (8.8--10.7 mg / dl, 4.3--5.2 mEq / L) with levels less than 2.1 mmol / l defined as hypocalcemia . Mildly low levels that develop slowly often have no symptoms . Otherwise symptoms may include numbness, muscle spasms, seizures, confusion, or cardiac arrest . </P> <P> Common causes include hypoparathyroidism and vitamin D deficiency . Others causes include kidney failure, pancreatitis, calcium channel blocker overdose, rhabdomyolysis, tumor lysis syndrome, and medications such as bisphosphonates . Diagnosis should generally be confirmed with a corrected calcium or ionized calcium level . Specific changes may be seen on an electrocardiogram (ECG). </P> <P> Initial treatment for severe disease is with intravenous calcium chloride and possibly magnesium sulfate . Other treatments may include vitamin D, magnesium, and calcium supplements . If due to hypoparathyroidism, hydrochlorothiazide, phosphate binders, and a low salt diet may also be recommended . About 18% of people who are being treated in hospital have hypocalcemia . </P> <P> The neuromuscular symptoms of hypocalcemia are caused by a positive bathmotropic effect due to the decreased interaction of calcium with sodium channels . Since calcium blocks sodium channels and inhibits depolarization of nerve and muscle fibers, reduced calcium lowers the threshold for depolarization . The symptoms can be recalled by the mnemonic "CATs go numb" - convulsions, arrhythmias, tetany, and numbness in the hands and feet and around the mouth . </P>

What is caused by hypocalcemia due to hypoparathyroidism