Mineral & Bone Disorder in Chronic Kidney Disease
What is mineral and bone disorder in chronic kidney disease (CKD)?
Mineral and bone disorder in CKD occurs when damaged kidneys and abnormal hormone levels cause calcium and phosphorus levels in a person’s blood to be out of balance. Mineral and bone disorder commonly occurs in people with CKD and affects most people with kidney failure receiving dialysis.
In the past, health care providers used the term “renal osteodystrophy” to describe mineral and hormone disturbances caused by kidney disease. Today, renal osteodystrophy only describes bone problems that result from mineral and bone disorder in CKD. Health care providers might use the phrase “chronic kidney disease mineral and bone disorder,” or CKD-MBD, to describe the condition that affects the bones, heart, and blood vessels.
What is chronic kidney disease?
Chronic kidney disease is kidney damage that occurs slowly over many years, often due to diabetes or high blood pressure. Once damaged, the kidneys can’t filter blood as they should. This damage can cause wastes to build up in the body and other problems that can harm a person’s health, including mineral and bone disorder.
Why are hormones and minerals important?
Hormones and minerals are important because they help bones stay strong. If a person’s hormones and minerals are out of balance, his or her bones can become weak and malformed. Healthy bones continuously rebuild, sometimes taking a slightly altered shape or structure. To grow and rebuild, bones need
- the hormone calcitriol—the active form of vitamin D
- parathyroid hormone
The kidneys play an important role in maintaining healthy bone mass and structure by balancing phosphorus and calcium levels in the blood. Healthy kidneys activate a form of vitamin D that a person consumes in food, turning it into calcitriol, the active form of the vitamin. Calcitriol helps the kidneys maintain blood calcium levels and promotes the formation of bone.
The kidneys also remove extra phosphorus, helping balance phosphorus and calcium levels in the blood. Keeping the proper level of phosphorus in the blood helps maintain strong bones.
The parathyroid glands, four pea-sized glands in the neck, create parathyroid hormone, or PTH. Parathyroid hormone plays an important role in controlling calcium levels in the blood. When the kidneys do not function properly, extra parathyroid hormone is released into the blood to move calcium from inside the bones into the blood.
What causes mineral and bone disorder in chronic kidney disease?
Chronic kidney disease causes mineral and bone disorder because the kidneys do not properly balance the mineral levels in the body. The kidneys
- stop activating calcitriol. The low levels of calcitriol in the body create an imbalance of calcium in the blood.
- do not remove the phosphorus in the blood properly, so phosphorus levels rise in the blood. The extra phosphorus pulls calcium out of the bones, causing them to weaken.
Another factor contributes to the cause of mineral and bone disorder. When the kidneys are damaged, the parathyroid gland releases parathyroid hormone into the blood to pull calcium from the bones and raise blood calcium levels. This response restores the balance of phosphorus and calcium; however, it also starves the bones of much-needed calcium.
What are the signs and symptoms of mineral and bone disorder in chronic kidney disease?
In adults, symptoms of mineral and bone disorder in CKD may not appear until bone changes have taken place for many years. For this reason, people often refer to the disease as a “silent crippler.” Eventually, a person with the condition may begin to feel bone and joint pain.
Mineral and Bone Disorder in Children with Chronic Kidney Disease
Mineral and bone disorder in CKD is most serious when it occurs in children because their bones are still developing and growing. Growing children can show symptoms of mineral and bone disorder even in the early stages of CKD. Slowed bone growth leads to short stature, which may remain with a child into adulthood. One deformity caused by mineral and bone disorder in CKD occurs when the legs bend inward or outward, a condition often referred to as "renal rickets." More information is provided in the NIDDK health topic, Growth Failure in Children with Kidney Disease. Find more about children’s bone health on the Eunice Kennedy Shriver National Institute of Child Health and Human Development website at www.nichd.nih.gov.
What are the complications of mineral and bone disorder in chronic kidney disease?
The complications of mineral and bone disorder in CKD include slowed bone growth and deformities, and heart and blood vessel problems.
Slowed Bone Growth and Deformities
Damaged kidneys must work harder to clear phosphorus from the body. High levels of phosphorus cause lower levels of calcium in the blood, resulting in the following series of events:
- When a person’s blood calcium level becomes too low, the parathyroid glands release parathyroid hormone.
- Parathyroid hormone removes calcium from bones and places it into the blood, raising a person’s blood calcium level at the risk of harming bones.
- A low calcitriol level also leads to an increased level of parathyroid hormone.
If mineral and bone disorder in CKD remains untreated in adults, bones gradually become thin and weak, and a person with the condition may begin to feel bone and joint pain. Mineral and bone disorder in CKD also increases a person’s risk of bone fractures.
Heart and Blood Vessel Problems
In addition to harming bones, mineral and bone disorder in CKD can cause problems in the heart and blood vessels:
- High levels of blood calcium can damage blood vessels and lead to heart problems.
- High phosphorus levels also can cause blood vessels to become like bone, leading to hardening of the arteries.
- High phosphorus levels also cause abnormal hormone regulation, even if the calcium level is acceptable.
Parathyroid hormone and another hormone made in the bones called FGF23 can also affect bone and heart health, leading to the following series of problems:
- When parathyroid hormone or FGF23 levels are high, a person can have heart problems.
- The complex hormone abnormalities that cause bone deformities can also harm a person’s heart and blood vessels.
How is mineral and bone disorder in chronic kidney disease diagnosed?
A health care provider diagnoses mineral and bone disorder in CKD with
- a family and medical history
- a physical exam
- a blood test
- a bone biopsy
- an x-ray
Family and Medical History
Taking a medical and family history is one of the first things a health care provider may do to help diagnose mineral and bone disorder in CKD. He or she will ask the patient or caretaker questions about when the patient was first diagnosed with CKD and whether any family members have also had mineral and bone disorder with or without CKD.
A physical exam may help diagnose mineral and bone disorder in CKD. During a physical exam, a health care provider usually examines a patient’s body for changes in bone structure.
A blood test involves drawing blood at a health care provider’s office or a commercial facility and sending the sample to a lab for analysis. The blood test shows levels of calcium, phosphorus, parathyroid hormone, and sometimes vitamin D.
A bone biopsy is a procedure that removes a piece of bone tissue for examination with a microscope. A health care provider performs the biopsy in a hospital with light sedation and local anesthetic. The health care provider uses imaging techniques such as ultrasound or a computerized tomography scan to guide the biopsy needle into the hip bone. A pathologist—a doctor who specializes in diagnosing diseases—examines the bone tissue in a lab. The test can show whether a person’s bone cells are building normal bone.
An x-ray is a picture created by using radiation and recorded on film or on a computer. The amount of radiation used is small. A radiographer performs the x-ray at a hospital or an outpatient center, and a radiologist—a doctor who specializes in medical imaging—interprets the images. Patients do not need anesthesia. The patient will lie on a table or stand during the x-ray. The technician will position the x-ray machine over the bone area. The patient will hold his or her breath as the x-ray machine takes the picture so that the picture will not be blurry. The radiographer may ask the patient to change position for additional pictures. An x-ray can show extra calcium in blood vessels.
Each of these tests can help the health care provider determine whether CKD or some other condition is causing the mineral and bone disorder and decide on a course of treatment.
How is mineral and bone disorder in chronic kidney disease treated?
Treating mineral and bone disorder in CKD includes preventing damage to bones by controlling parathyroid hormone levels through changes in eating, diet, and nutrition; medications and supplements; and dialysis. If these treatments do not bring parathyroid hormone levels under control, a health care provider may remove a person’s parathyroid glands surgically, a procedure called a parathyroidectomy.
Eating, Diet, and Nutrition
Changes in diet can treat mineral and bone disorder in CKD. Reducing dietary intake of phosphorus is one of the most important steps in preventing bone disease. Most foods contain phosphorus; however, processed and packaged foods contain especially high levels of phosphorus. Food producers use phosphorus as an additive to preserve the food on the shelf. People who have CKD or are on dialysis should avoid packaged foods containing ingredients that include the letters PHOS. A renal dietitian can help develop a dietary plan to control phosphorus levels in the blood. Some drinks and natural foods also contain high amounts of phosphorus, including
- dark sodas
- dried beans
- peanut butter
More information is provided in the NIDDK health topics, How To Read a Food Label: Tips for People with Chronic Kidney Disease and Phosphorus: Tips for People with Chronic Kidney Disease.
Medications and Supplements
Medications protect the bones by restoring the proper balance of minerals and hormones. If the kidneys do not make adequate amounts of calcitriol, a health care provider may prescribe synthetic calcitriol as a pill (Rocaltrol) or, for dialysis patients, in an injectable form (Calcijex). Calcitriol helps reduce parathyroid hormone levels. Medications called doxercalciferol (Hectorol) and paricalcitol (Zemplar) act like calcitriol because they are also activated forms of vitamin D. A health care provider may prescribe a calcium supplement in addition to calcitriol or another activated form of vitamin D.
Certain forms of vitamin D—available by prescription or as over-the-counter vitamin supplements—require activation by a person’s kidneys before they can act as calcitriol does. However, the benefits of some of these not-yet-activated forms of vitamin D—for example, ergocalciferol (Calciferol, Drisdol) or cholecalciferol (Delta D3)—are unclear. To help ensure coordinated and safe care, people should discuss their use of alternative medications, including use of vitamin and mineral supplements, with their health care provider.
Cinacalcet hydrochloride (Sensipar) belongs to another class of prescription medications called calcimimetics. Cinacalcet lowers parathyroid hormone levels by imitating calcium’s effects on the parathyroid gland. Generally, this medication is used only in people on dialysis.
Often, health care providers will prescribe medications called phosphate binders—such as calcium carbonate (Tums), calcium acetate (PhosLo), sevelamer carbonate (Renvela), or lanthanum carbonate (Fosrenol)—to take with meals and snacks to bind phosphorus in the bowel. These medications decrease the absorption of phosphorus into the blood.
Dialysis is the process of filtering wastes and extra fluid from the body by means other than the kidneys. The two forms of dialysis are hemodialysis and peritoneal dialysis:
- Hemodialysis uses a machine to circulate a person’s blood through a filter outside the body. The blood passes from a patient’s body through a needle, at nearly 1 pint per minute. The blood then travels through a tube that takes it to the filter, called a dialyzer. Inside the dialyzer, the blood flows through thin fibers that filter out wastes and extra fluid. After the machine filters the blood, it passes back to the body through another tube. More information is provided in the NIDDK health topic, Treatment Methods for Kidney Failure: Hemodialysis.
- Peritoneal dialysis uses the lining of the abdomen to filter a person’s blood inside the body. A soft tube called a catheter is placed in the patient’s abdomen a few weeks before peritoneal dialysis begins. A person uses the catheter to fill the empty space inside the abdomen with dialysis solution—a kind of salty water—from a plastic bag. While inside the body, the dialysis solution absorbs wastes and extra fluid. After a few hours, the person drains the used dialysis solution into another bag for disposal. The person then restarts the process with a fresh bag of dialysis solution. More information is provided in the NIDDK health topic, Treatment Methods for Kidney Failure: Peritoneal Dialysis.
Increasing a person’s dialysis dose can help control the blood phosphorus level. In hemodialysis, the health care provider can adjust the dose by increasing how quickly the blood flows to and from the dialyzer. Another way to adjust the dose involves increasing the time of a person’s dialysis session or the number of sessions. In peritoneal dialysis, using more dialysis solution in each fill or increasing the number of fills each day increases the dose. More information is provided in the NIDDK health topics:
If diet, medications, and dialysis can’t control parathyroid hormone levels, a surgeon can remove one or more of the parathyroid glands. He or she performs the procedure using general anesthesia.
A good treatment program, including a low-phosphorus diet, appropriate medications, adequate dialysis, and, if necessary, surgery, can improve the body’s ability to repair bones damaged by mineral and bone disorder in CKD. Overall, people can improve their bone health by exercising and not smoking. People should consult a health care provider before beginning any exercise program.
Points to Remember
- Mineral and bone disorder in chronic kidney disease (CKD) occurs when damaged kidneys and abnormal hormone levels cause calcium and phosphorus levels in a person’s blood to be out of balance. Mineral and bone disorder commonly occurs in people with CKD and affects most people with kidney failure receiving dialysis.
- Chronic kidney disease is kidney damage that occurs slowly over many years, often due to diabetes or high blood pressure. Once damaged, the kidneys can’t filter blood as they should.
- Hormones and minerals are important because they help bones stay strong. If a person’s hormones and minerals are out of balance, his or her bones can become weak and malformed.
- Parathyroid hormone plays an important role in controlling calcium levels in the blood. When kidneys do not function properly, extra parathyroid hormone is released in the blood to move calcium from inside the bones into the blood.
- Chronic kidney disease causes mineral and bone disorder because the kidneys do not properly balance the mineral levels in the body. The kidneys stop activating calcitriol and do not remove the phosphorus in the blood properly.
- The complications of mineral and bone disorder in CKD include slowed bone growth and deformities, and heart and blood vessel problems.
- Treating mineral and bone disorder in CKD includes preventing damage to bones by controlling parathyroid hormone levels through changes in eating, diet, and nutrition; medications and supplements; and dialysis.
- Reducing dietary intake of phosphorus is one of the most important steps in preventing bone disease.
- If diet, medications, and dialysis can’t control parathyroid hormone levels, a surgeon can remove one or more of the parathyroid glands.
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About the Kidney Failure Series
You and your doctor will work together to choose a treatment that's best for you. The publications of the NIDDK Kidney Failure Series can help you learn about the specific issues you will face.
- What I need to know about Kidney Failure and How it’s Treated
- Treatment Methods for Kidney Failure: Hemodialysis
- Treatment Methods for Kidney Failure: Peritoneal Dialysis
- Treatment Methods for Kidney Failure: Kidney Transplantation
- Kidney Failure: Eat Right to Feel Right on Hemodialysis
- Kidney Failure: What to Expect
- Vascular Access for Hemodialysis
- Hemodialysis Dose and Adequacy
- Peritoneal Dialysis Dose and Adequacy
- Amyloidosis and Kidney Disease
- Anemia in Chronic Kidney Disease
- Financial Help for Treatment of Kidney Failure
Learning as much as you can about your treatment will help make you an important member of your health care team.
This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.
The NIDDK would like to thank:
Sharon Moe, M.D., Indiana University School of Medicine for reviewing this publication.