Chronic Kidney Disease—Mineral and Bone Disorder
Kidney Health Care - David Mangusan Jr., PTRP
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Chronic kidney disease—mineral and bone disorder (CKD-MBD) occurs when the kidneys fail to maintain proper levels of phosphorus and calcium in the blood. The condition commonly occurs in people with kidney disease and affects almost all patients who undergo dialysis.
CKD-MBD is more serious when it occurs in children because their bones are still rowing. This can cause slowing down of bone growth and can also cause bone deformities. For example, children with CKD-MBD can experience inward or outward deformity of the legs. This type of deformity is referred to as “renal rickets.” Growth is also affected which can result in short stature.
In adults, bone changes from CKD-MBD can begin many years before symptoms appear. If CKD-MBD is left untreated, the bones slowly become thin and weak, which can cause bone and joint pains. Because CKD-MBD causes thinning and weakening of bones, there is a risk of developing bone fractures.
In the past, doctors used the term renal osteodystrophy to describe the mineral and hormone disturbances caused by kidney disease. Now, renal osteodystrophy is used only to describe the bone problems that occur as a result of CKD-MBD.
Role of Hormones and the Kidneys in Maintaining Normal Bone Health
The kidneys play an important role in maintaining normal bone mass and structure. They help to balance levels of calcium and phosphorus in the blood. Also, the kidneys help ensure that the vitamin D a person receives from sunlight and food becomes activated.
Calcium is a mineral that builds and strengthens bones. Calcium is found in many foods, particularly milk and other dairy products. When levels of calcium become too low in the blood, the parathyroid glands release a hormone called parathyroid hormone (PTH). This hormone draws calcium from bones to raise blood calcium levels. Too much PTH in the blood will remove too much calcium from the bones; over time, the constant removal of calcium weakens the bones.
Phosphorus, which is found in most foods, also helps regulate calcium levels in the bones. Healthy kidneys remove excess phosphorus from the blood. When the kidneys stop working normally, phosphorus levels in the blood can become too high, leading to lower levels of calcium in the blood. Low blood calcium levels can cause the release of too much PTH, which results in the loss of calcium from the bones.
Normally, the kidneys produce calcitriol, a form of vitamin D, to help the body absorb dietary calcium into the blood and the bones. However, when levels of calcitriol declines, PTH levels increase, and calcium is removed from the bones. Calcitriol and PTH work together to keep calcium balance normal and bones healthy. In a patient with kidney failure, the kidneys stop making calcitriol. The body then can't absorb calcium from food and starts removing it from the bones. As a result, the bones become weak and brittle, making the person more prone to having bone fractures.
Diagnosis of CKD-MBD
To diagnose CKD-MBD, your doctor may take a sample of your blood. The blood sample will be used to determine levels calcium, phosphorus, PTH, and sometimes vitamin D in your blood. Your doctor may also recommend a biopsy of your bone. This will help to determine if bone cells are normally building bone tissues. Bone biopsy involves taking a sample of bone from your hip, which is then analyzed under a microscope. The procedure is done under a local anesthesia.
Treatment of CKD-MBD
Controlling levels of parathyroid hormone prevents damage to bones. Overactive parathyroid glands are usually controllable with changes in the diet, dialysis treatment, or medication.
Exercising can improve your overall bone health. However, people on dialysis should consult a health care provider before beginning any exercise program.
Quit smoking
References:
National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC). Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH). NIH Publication No. 09–4630, February 2009
Tortora, G. and Grabowski, S.: PRINCIPLES OF ANATOMY AND PHYSIOLOGY. 10th ed. John Wiley and Sons, Inc., 2003.
Seeley, R., Stephens, T., and Tate, P.: Essentials of Anatomy and Physiology.5th ed.Mc-Graw-Hills, Inc., 2005
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CKD-MBD is more serious when it occurs in children because their bones are still rowing. This can cause slowing down of bone growth and can also cause bone deformities. For example, children with CKD-MBD can experience inward or outward deformity of the legs. This type of deformity is referred to as “renal rickets.” Growth is also affected which can result in short stature.
In adults, bone changes from CKD-MBD can begin many years before symptoms appear. If CKD-MBD is left untreated, the bones slowly become thin and weak, which can cause bone and joint pains. Because CKD-MBD causes thinning and weakening of bones, there is a risk of developing bone fractures.
In the past, doctors used the term renal osteodystrophy to describe the mineral and hormone disturbances caused by kidney disease. Now, renal osteodystrophy is used only to describe the bone problems that occur as a result of CKD-MBD.
Role of Hormones and the Kidneys in Maintaining Normal Bone Health
The kidneys play an important role in maintaining normal bone mass and structure. They help to balance levels of calcium and phosphorus in the blood. Also, the kidneys help ensure that the vitamin D a person receives from sunlight and food becomes activated.
Calcium is a mineral that builds and strengthens bones. Calcium is found in many foods, particularly milk and other dairy products. When levels of calcium become too low in the blood, the parathyroid glands release a hormone called parathyroid hormone (PTH). This hormone draws calcium from bones to raise blood calcium levels. Too much PTH in the blood will remove too much calcium from the bones; over time, the constant removal of calcium weakens the bones.
Phosphorus, which is found in most foods, also helps regulate calcium levels in the bones. Healthy kidneys remove excess phosphorus from the blood. When the kidneys stop working normally, phosphorus levels in the blood can become too high, leading to lower levels of calcium in the blood. Low blood calcium levels can cause the release of too much PTH, which results in the loss of calcium from the bones.
Normally, the kidneys produce calcitriol, a form of vitamin D, to help the body absorb dietary calcium into the blood and the bones. However, when levels of calcitriol declines, PTH levels increase, and calcium is removed from the bones. Calcitriol and PTH work together to keep calcium balance normal and bones healthy. In a patient with kidney failure, the kidneys stop making calcitriol. The body then can't absorb calcium from food and starts removing it from the bones. As a result, the bones become weak and brittle, making the person more prone to having bone fractures.
Diagnosis of CKD-MBD
To diagnose CKD-MBD, your doctor may take a sample of your blood. The blood sample will be used to determine levels calcium, phosphorus, PTH, and sometimes vitamin D in your blood. Your doctor may also recommend a biopsy of your bone. This will help to determine if bone cells are normally building bone tissues. Bone biopsy involves taking a sample of bone from your hip, which is then analyzed under a microscope. The procedure is done under a local anesthesia.
Treatment of CKD-MBD
Controlling levels of parathyroid hormone prevents damage to bones. Overactive parathyroid glands are usually controllable with changes in the diet, dialysis treatment, or medication.
DietOther things you can do
One of the most important steps in preventing bone disease is reducing the intake of phosphorus. Your renal dietician can help you plan a diet to control phosphorus levels in your blood.
Your doctor may prescribe medications called phosphate binders to be taken with meals and snacks. Phosphate binders help in decreasing absorption of phosphorus into the blood by binding with phosphorus in the intestine. Examples of phosphate binders are calcium carbonate (Tums), calcium acetate (PhosLo), sevelamer hydrochloride (Renagel), and lanthanum carbonate (Fosrenol). (National Kidney and Urologic Diseases Information Clearinghouse, National Institutes of Health, February 2009)
Dialysis
Increasing dialysis dose by increasing patient’s flow rate or rate in treatment may also help control phosphorus.
Other medications
If your kidneys are not making enough calcitriol, your doctor may prescribe synthetic calcitriol or other forms of vitamin D as a pill or in an injectable form.
Surgery
Surgery to remove the parathyroid glands may be recommended by your doctor if your PTH levels cannot be controlled with medications or diet.
Exercising can improve your overall bone health. However, people on dialysis should consult a health care provider before beginning any exercise program.
Quit smoking
References:
National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC). Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH). NIH Publication No. 09–4630, February 2009
Tortora, G. and Grabowski, S.: PRINCIPLES OF ANATOMY AND PHYSIOLOGY. 10th ed. John Wiley and Sons, Inc., 2003.
Seeley, R., Stephens, T., and Tate, P.: Essentials of Anatomy and Physiology.5th ed.Mc-Graw-Hills, Inc., 2005
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