Calcium Metabolism

1. Calcium
2. Calcium Regulation
3. Quiz

• Calcium has a range of functions, including regulation of heart rhythm, kidney function, muscle function, and nerve function
• Parathyroid hormone is produced in the parathyroid gland, and functions to increase calcium concentrations in acute conditions
• Calcitriol is an activated form of vitamin D, and functions to increase calcium concentrations over longer periods of time
• Calcitonin is produced in the parafollicular cells of the thyroid gland, and acts to oppose the action of parathyroid hormone

Calcium is one of the most important ions in the body, having many functions:

• Regulation of heart rhythm
• Maintaining muscle function
• Maintaining kidney function 
• Maintaining nerve function
• Maintaining bones and teeth
• Influences blood clotting, blood pressure, and cholesterol
• Hormone and enzyme activity
• Intracellular signalling pathways

The majority of calcium found in adults is stored in bone as hydroxyapatite crystals. The skeleton is a major reserve of calcium, and acts to buffer serum calcium levels through releasing calcium phosphate into the interstitium when required (serum calcium levels are normally between 2.2-2.6mM). Dairy is the main source of dietary calcium. 

In plasma, calcium exists in one of three forms;

• As a free ionised species (biologically active calcium)
• Associated with serum proteins at their anionic sites (particularly albumin)
• Complexed with low-molecular-weight organic anions 

Preview the Calcium Metabolism quiz