Calcium is the most important mineral found in bone. It is obtained primarily from dietary sources. The kidneys are important in the regulation of blood calcium levels. When blood calcium increases, there is increased excretion of calcium into the urine. According to a May 2006 "Agency for Healthcare Research and Quality" article, the prolonged consumption of calcium at doses greater than or equal to 1 g per day increases the likelihood for developing kidney stones.
Calcium Regulation
The thyroid and parathyroid glands are the two most important glands involved with calcium regulation; these two glands are located in the neck. When blood calcium level increases, the thyroid gland releases calcitonin, a hormone that increases the deposition of calcium into bone. When blood calcium level decreases, the parathyroid gland releases the parathyroid hormone, or PTH, which results in increased bone breakdown and release of calcium to the blood. PTH also acts in the kidneys to prevent or slow the excretion of calcium. As blood calcium increases, PTH secretion is decreased, thereby resulting in increased calcium excretion.
Risk Factors for Kidney Stone Development
Having hypercalcemia, or high blood calcium, does not guarantee kidney stone formation; any cause of high blood calcium is simply a predisposition for kidney stone development. Other factors, such as low urine volume and high dietary intake of proteins and sodium, increase the likelihood for kidney stone development. Diseases that affect the small intestines and surgical resection of the small intestines also favor the formation of kidney stones.
Clinical Presentation of Kidney Stones
A person with kidney stones will likely experience a sudden onset of pain in the loin; this pain often radiates to other regions of the body, including the groin and testes. The pain is typically constant and steadily increases to a peak after several minutes. During the episode of pain, the person will become restless and will try relieving the pain by changing positions, to no avail. Kidney stones are also associated with increased frequency of urination, urinary discomfort and sometimes blood in the urine.
Prevention of Kidney Stones
Prevention of kidney stones involves the modification of environmental and dietary factors. Avoid consuming high amounts of sodium and protein. Increasing water intake can help increase urine volume. Hypercalcemia must be addressed by treating the underlying health conditions; for example, primary hyperparathyroidism, or elevated blood PTH due to overactive parathyroid glands, can be treated by surgically removing the parathyroid glands.
References
- "Agency for Healthcare Research and Quality"; Evidence Reports: Multivitamin/Mineral Supplements and Prevention of Chronic Disease; H.Y. Huang, et al.; May 2006
- "Davidson's Principles & Practice of Medicine"; Nicholas A. Boon; 2006
- "Harrison's Principles of Internal Medicine"; Dennis L. Kasper, M.D., et al.; 2005
