Symptoms can range from quite mild (tingling in the hands, fingers, and around the mouth) to more severe forms of muscle cramps.  The most severe symptoms are tetany (severe muscle cramping of the entire body) and convulsions (this is very rare).

Parathyroid gland insufficiency is quite rare, but it can occur in several well-defined ways.  The most common cause of hypoparathyroidism is the loss of active parathyroid tissue following thyroid or parathyroid surgery.  Even more rare is a defect present at birth (congenital), where a person is born without parathyroid glands.  Occasionally, the specific cause of hypoparathyroidism cannot be determined.