The serum level of calcium is closely regulated within a fairly limited range in the human body.

[1] Inherited hypoparathyroidism is rare and is due to a mutation in the calcium sensing receptor.

Low vitamin D in the body can lead to a lack of calcium absorption and secondary hyperparathyroidism (hypocalcemia and raised parathyroid hormone).

[2] Approximately 10% of individuals with cancer experience hypercalcemia due to malignancy.

[2] Symptoms of hypercalcemia include anorexia, nausea, vomiting, constipation, abdominal pain, lethargy, depression, confusion, polyuria, polydipsia and generalized aches and pains.