Calcium (Ca+), a positive ion in the body, is necessary for neuromuscular processes, bone mineralization, and hormonal secretion. The parathyroid gland and vitamin D are responsible for calcium regulation in the body. In the blood, about half of calcium travels in ion form, the other half is bound to proteins like albumin. When albumin levels are low, calcium levels will appear lower. Calcium has an important relationship with phosphorus: they are inversely proportional.