Understanding Blood Calcium Levels

Mallorca (Majorca) is one of Spain's Islands in the Mediterranean. (Dr. Noorali Bharwani)
Mallorca (Majorca) is one of Spain's Islands in the Mediterranean. (Dr. Noorali Bharwani)

Calcium and vitamin D are the two most important nutrients for bone health. Calcium has many other important functions in the body.

Calcium is necessary for life.

In addition to building bones and keeping them healthy, calcium helps our blood clot, helps nerves send messages and helps muscles contract. About 99 percent of the calcium in our bodies is in bones and teeth.

Each day, we lose calcium through our skin, nails, hair, sweat, urine and feaces. But our bodies cannot produce new calcium. That is why it is important to get calcium from the food we eat. When we do not get enough calcium for our body’s needs, it is taken from our bones. This makes bones weak.

A natural source of calcium in our diet comes from milk and milk alternatives. It is important to drink milk everyday. Calcium is also found in dark leafy greens, legumes and canned salmon.

Role of parathyroid hormone

Excessive calcium (hypercalcemia) most commonly results from overactive parathyroid glands. These four tiny glands are each about the size of a grain of rice and are located on or near the thyroid gland. Certain types of cancer, other medical disorders, some medications, and excessive use of calcium and vitamin D supplements can also cause hypercalcemia.

Overactive parathyroid gland (hyperparathyroidism) can raise calcium levels. The role of the parathyroid hormone is to help maintain an appropriate balance of calcium in the bloodstream and in tissues that depend on calcium for proper function.

Hyperparathyroidism is often diagnosed before signs or symptoms of the disorder are apparent. When symptoms do occur it is because of damage or dysfunction in other organs due to high calcium levels in the blood, urine, or too little calcium in bones.

Hyperparathyroidism can cause a wide variety of symptoms. It can make bones fragile (osteoporosis), create kidney stones, increase urination, cause abdominal pain, weakness, depression and forgetfulness. It can also cause aches and pains, nausea, vomiting or loss of appetite.

When your calcium levels are low, your parathyroid glands secrete parathyroid hormone to restore the balance. Parathyroid hormone raises calcium levels by releasing calcium from your bones and increasing the amount of calcium absorbed from your small intestine. Parathyroid hormone also acts on the kidneys, resulting in decreased excretion of calcium.

The physiology and balancing acts of calcium, phosphorus, vitamin D and parathyroid hormone is very interesting and not easy to comprehend.

To summarize:

Bones play an important role in blood calcium levels, which must be maintained within narrow limits to maintain bodily functions.

Bones are the major storage site for calcium. The movement of calcium into and out of bone helps to maintain blood calcium levels.

Parathyroid hormone and calcitonin also help regulate blood calcium levels.

Parathyroid hormone promotes the absorption of calcium by the small intestines, which also increases blood calcium levels.

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