Bone disease and kidney disease
The kidneys perform a variety of jobs. Keeping mineral levels within the body in balance is just one of them. There is a correlation between bone disease and kidney disease. Inside the skeleton, calcium and phosphorus are stored — the key minerals for maintaining bone health. The inside of a person’s skeleton can be compared to a construction site, always working at building bone up or tearing it down.
Calcium, bone disease and kidney disease
The body normally has an ample supply of calcium with 99% stored in the bones and teeth. It is the main “construction material” used to make strong, healthy bones. Dietary calcium absorbed from the intestines is used to make new bone cells, and help supply a source of calcium to be used by the body as needed. A doctor may prescribe calcium supplements along with vitamin D to increase calcium absorption. Making sure blood calcium level is adequate in people with kidney disease can help prevent or manage renal bone disease.
Parathyroid hormone (PTH), bone disease and kidney disease
Small parathyroid glands inside the neck manufacture a hormone called parathyroid hormone, or PTH, that helps regulate calcium in the blood. If the level of calcium gets too low, PTH will stimulate the kidneys to activate vitamin D, which increases absorption of dietary calcium. PTH also releases calcium from the bones. The parathyroid glands make too much PTH in chronic kidney disease. When PTH is too high, the bones begin to break down, leading to renal bone disease. Calcium and phosphorus are released from the bones and cause calcifications in blood vessels, organs and soft tissues of the body.
Phosphorus, bone disease and kidney disease
Phosphorus works hand-in-hand with calcium to build bones and is stored mainly in bones and teeth. Unfortunately, chronic kidney disease can cause phosphorus to build up in the blood, which also causes an increase in PTH and more calcium to be released from the bones. To manage renal bone disease due to high phosphorus, a kidney friendly eating plan, limited in phosphorus is generally prescribed. The doctor may also prescribe a phosphate binder to prevent absorption of excess phosphorus.
Vitamin D, bone disease and kidney disease
Vitamin D increases the amount of calcium in the blood, but not before it becomes active. When a person gets vitamin D from the sun, foods or supplements, the body must transform it into calcitriol, which is also called activated vitamin D. This process occurs in the kidneys and is regulated by PTH. Kidney disease causes kidneys to lose their ability to activate vitamin D into calcitriol, causing excess PTH production and calcium and phosphorus loss from the bones. To prevent this, an active vitamin D supplement can be prescribed to prevent and treat renal bone disease in people with kidney disease.
What can I do about bone disease and kidney disease?
Bone disease can be slowed and even stopped in its tracks with the right treatment. In addition to medications to help correct calcium, phosphorus and PTH levels, a kidney-friendly eating plan will help. Reducing phosphorus in the diet helps keep PTH lower and prevent high phosphorus levels in the blood. A renal dietitian can determine an eating plan to manage kidney-related bone disease. Knowing which foods are low phosphorus foods and which are high-phosphorus foods is a good start. Talk to your doctor about arranging a meeting with a renal dietitian who specializes in the diet for kidney disease and understands renal bone disease.
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