The human body contains more than 2.2 pounds of calcium, mostly in the bones. As most people know, calcium is vital for human health.

In fact, it is such an important mineral that our bodies are designed to use various hormones to ensure adequate calcium levels in both the bloodstream and the bones.

The hormones responsible for maintaining calcium levels include vitamin D, calcitonin, and parathyroid hormone.

Specifically, vitamin D enhances absorption of calcium from the gastrointestinal tract; calcitonin stimulates the absorption of calcium into bones; and parathyroid hormone causes calcium to be released by the bones.

The complex interplay between these three hormones are responsible for ensuring:

• Adequate calcium absorption

• Integration of calcium into the bones

• Normal serum calcium levels

Parathyroid hormone — which is secreted by the parathyroid glands — increases the concentration of calcium in the bloodstream by releasing calcium from the bones. This process is called “bone resorption.”

In the kidneys, parathyroid increases reabsorption of calcium. In other words, it decreases calcium excretion in the urine.

Hyperparathyroidism — an excess of parathyroid hormone — is known to cause both osteopenia and osteoporosis.

In treating osteoporosis, it is important to closely monitor parathyroid hormone levels. It should be supplemented only when levels are very low.