Why are kidneys important for bone health?
Healthy kidneys do many important jobs. They remove wastes and extra fluid from your body, help make red blood cells, and help keep bones strong. They also help to keep the right amount of minerals in your blood. Minerals are nutrients that your body needs to stay healthy.
When you have kidney disease or kidney failure, your kidneys cannot do these important jobs well. As a result, you may develop mineral and bone disorder. It is a common problem in people with kidney disease, and it affects almost everyone with kidney failure.
What is mineral and bone disorder?
Mineral and bone disorder related to kidney disease happens when there is an imbalance in your blood levels of calcium and phosphorus. This mineral imbalance can affect your bones, heart and blood vessels.
How does kidney disease and kidney failure lead to bone and heart disease?
When too much kidney function is lost, your kidneys can no longer filter out extra phosphorus and remove it from the body in the urine. Over time, phosphorus from the foods you eat can build up to high levels in your blood.
Healthy kidneys also change vitamin D from sunlight and the foods you eat into active vitamin D that your body can use. When kidneys fail there is a short supply of active vitamin D. This causes calcium and phosphorus to get out of balance.
When the blood phosphorus level goes up and blood vitamin D level goes down, your body makes too much parathyroid hormone (PTH). High PTH levels cause calcium to move from your bones into your blood. As calcium leaves your bones they become weaker, more brittle, and are more likely to break. Some calcium may also end up in the heart and blood vessels. This may cause or worsen heart disease.
What are the signs and symptoms of mineral and bone disorder?
Mineral and bone disorder can cause you to have:
- Itchy skin
- Bone pain
- Weak bones that break easily
- Blocked blood vessels
- Heart problems
- Nerve problems
- Difficulty fighting off germs
How do I know if I have mineral and bone disorder?
- You will have blood tests to check your blood levels of calcium, phosphorus, PTH and vitamin D.
- Some people may need to have a bone biopsy. A bone biopsy is a sample of bone taken for study.
- Your healthcare provider may order an x-ray of your abdomen, or an echocardiogram of your heart to check if mineral imbalance has affected your heart and blood vessels.
How do you treat mineral and bone disorder?
Many people with kidney disease or kidney failure need treatment for high blood phosphorus or PTH levels. Your healthcare provider will order the treatment that is right for you.
- Lower phosphorus diet
Eating a lower phosphorus diet helps to keep your blood phosphorus in the right range. Speak with your kidney dietitian on ways to limit dietary phosphorus intake.
- Phosphate binders
Phosphate binders and phosphate absorption inhibitors are medicines that help to keep blood phosphorus levels under control.
- Vitamin D
Your body needs the active form of vitamin D. Your healthcare provider will decide which type of vitamin D medicine is right for you
Calcimimetcs are medicines often used when blood PTH, calcium and phosphorus levels are too high in people on dialysis.
- Calcium supplements
Speak to your healthcare provider before taking a calcium supplement. The results of your blood tests will help show if you need to take extra calcium.
Some people with high PTH levels need surgery to remove some or all of the parathyroid gland.
The exercises that may be most helpful are called strengthening and weight-bearing exercise. Check with your healthcare provider before starting an exercise program.
To read more about mineral and bone disorder, click here.
Reviewed June, 2014
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© 2015 National Kidney Foundation. All rights reserved. This material does not constitute medical advice. It is intended for informational purposes only. Please consult a physician for specific treatment recommendations.