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Bone Loss and Kidney Disease

There are a lot of repercussions to kidney disease. One of them is bone loss and the resultant problems. (Read about "Skeletal System") Renal osteodystrophy is the medical term when your kidneys (Read about "Kidney Disease") fail to keep a proper balance of calcium (Read about "Calcium") and phosphorus in your blood. The problem is very common in kidney disease patients. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says that 90 percent of dialysis patients are affected. (Read about "End Stage Renal Disease")

What's causes the problem

Your kidneys play a crucial role in balancing the amount of calcium and phosphorous in your blood stream. Calcium is a mineral that builds and strengthens bones. If calcium levels in the blood become too low, four small endocrine glands in the neck called the parathyroid glands release a hormone called parathyroid hormone (PTH). (Read about "Parathyroid Glands") This hormone draws calcium from the 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 also helps regulate calcium levels in the bones. Most of the foods we eat contain phosphorus. The kidneys remove the excess that we don't need. When the kidneys are damaged and they don't take the extra phosphorus out, it leads to less calcium in your blood stream. Calcium is then pulled from the bones to keep the levels up.

Your kidneys also have the job of turning the vitamin D you eat and your body produces into what is called calcitriol or "active" form that can be used. (Read about "Vitamins & Minerals") Active vitamin D is important for bone health as well. If calcitriol levels drop too low, PTH levels increase, and calcium is removed from the bones.

Because of all the kidneys do, kidney disease can lead to bone loss. This is very serious in children because their bones are still growing. The condition slows bone growth and causes deformities. Postmenopausal woman and the elderly also are at greater risk because they already face bone loss. (Read about "Age and Bone Loss" "Menopause")

To diagnose renal osteodystrophy, your doctor may take a sample of your blood to measure levels of calcium, phosphorus, PTH and calcitriol. The doctor may perform a bone biopsy to see how dense your bones are. A bone biopsy is done under local anesthesia (Read about "Anesthesia") and involves removing a small sample of bone and analyzing it under a microscope. (Read about "Biopsy") Determining the cause of renal osteodystrophy helps the doctor decide on a course of treatment.

Treatments

Dietary changes and supplements are an important form of treatment according to the National Kidney Foundation (NKF). Reducing the amount of phosphorus in your diet is one of the first steps according to NKF. Foods high in phosphorous according to NIDDK and NKF include:

• dairy products such as milk and cheese
• dried beans and peas
• nuts
• peanut butter
• cocoa
• dark sodas such as colas
• beer

NKF and NIDDK also say your doctor may suggest taking calcium and D supplements, synthetic calcitriol as a pill or in an injectable form, medication to control PTH levels and/or medications that bind to phosphorus before your body takes it up.

Related Information:

    Osteoporosis

    Calcium and Osteoporosis

    Calcium

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