Hypocalcemia is the medical term for low serum calcium. Causes include hypoparathyroidism, vitamin D deficiency, hyperphosphatemia and acute pancreatitis, according to Christopher O'Callaghan in the book "The Renal System at a Glance." When the renal system isn't functioning or more phosphates enter the bloodstream than the kidneys can handle, the body excretes phosphates in the stool, blocking calcium absorption and causing hypocalcemia. Hypocalcemia most often occurs in newborns, either within the first two days of life or after five to 10 days. Hypocalcemia in newborns can result from feeding your child formula, which can contain high levels of phosphates.
Calcium is necessary for the regulation of muscle response and nerve function. Accordingly, a lack of serum calcium can result in muscle stiffness, twitches and tremors. Owing to the subtlety of these symptoms, they may not appear conspicuous enough to indicate a serious condition, particularly in babies. Hypocalcemia may cause tingling or numbing of your fingers and toes. Hypocalcemia can also cause a prolonged QT interval, a type of heart arrhythmia that manifests as an abnormally long interval between the high points and low points on an electrocardiogram. Other cardiovascular effects include low blood pressure and congestive heart failure.
Nerve-related signs of hypocalcemia include Weiss's sign and Trousseau's sign. Weiss's sign refers to a facial nerve hypersensitivity in which one half of the face tenses when a doctor taps on the jaw muscle on that side. Trousseau's sign, which is more a better indicator of hypocalcemia than Weiss's sign, occurs when the hands and forearm muscles spasm in response to a diagnostic cutoff in blood circulation.
Low serum calcium can affect your sense of overall well-being, resulting in behavioral changes. Among these effects are lethargy, anxiety, depression and irritability. If you have hypocalcemia, you may also exhibit loss of appetite and jitters. These issues may appear indistinct and you may simply feel an overall sense that something is wrong. Although these symptoms could be attributable to anything, they more substantively indicate hypocalcemia in the presence of associated physiological or neurological symptoms.
The most acute symptom of hypocalcemia is seizure. Because calcium is necessary for neurological function and development, low serum calcium can cause brain damage, resulting in serious neurological complications. Because hypocalcemia can be difficult to identify, particularly in infants, you may not notice it until the onset of these serious symptoms.