Editing Calcium (section)

===Abnormal serum levels===
Excess intake of calcium may cause [[hypercalcemia]]. However, because calcium is absorbed rather inefficiently by the intestines, high serum calcium is more likely caused by excessive secretion of parathyroid hormone (PTH) or possibly by excessive intake of vitamin D, both of which facilitate calcium absorption. All these conditions result in excess calcium salts being deposited in the heart, blood vessels, or kidneys. Symptoms include anorexia, nausea, vomiting, memory loss, confusion, muscle weakness, increased urination, dehydration, and metabolic bone disease.{{sfn|Hluchan|Pomerantz|2005|pp = 489–94}}

Chronic hypercalcaemia typically leads to [[calcification]] of soft tissue and its serious consequences: for example, calcification can cause loss of elasticity of [[vascular wall]]s and disruption of laminar blood flow—and thence to [[Vulnerable plaque|plaque rupture]] and [[thrombosis]]. Conversely, inadequate calcium or vitamin D intakes may result in [[hypocalcemia]], often caused also by inadequate secretion of parathyroid hormone or defective PTH receptors in cells. Symptoms include neuromuscular excitability, which potentially causes [[tetany]] and disruption of conductivity in cardiac tissue.{{sfn|Hluchan|Pomerantz|2005|pp = 489–94}}