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Keeping Bones Healthy with Kidney Disease
Healthy bones are essential for good body structure and mobility. The human skeleton provides the framework for our body, supports our body weight, and protects our internal organs. Our bones also store two important minerals – calcium and phosphorus.
People with kidney disease often have imbalanced levels of calcium, phosphorus, parathyroid hormone (PTH) and activated vitamin D. This imbalance disrupts bone cells, causing a bone disease called renal osteodystrophy.
If untreated, renal osteodystrophy can cause weak, easily-broken bones, calcification of the soft tissues (such as the heart), and even death. Common symptoms are bone and joint pain, bone deformation, bone fractures and poor mobility. Since these symptoms often do not appear until a patient has been on dialysis for a few years, it is important to monitor blood levels of calcium, phosphorus, PTH and vitamin D to detect the disease.
Calcium and PTH
Calcium is essential for bone growth and strength. Dairy products like milk, yogurt and cheese are good sources of calcium. However, these items are usually too high in phosphorus to be included in a kidney diet except for in small amounts. When blood calcium levels are low, your parathyroid glands release a hormone called parathyroid hormone (PTH). This hormone pulls calcium out of your bones and into your bloodstream. Over time, as more calcium is pulled from your bones, your bones become very weak. If your blood calcium levels are too low, your doctor may prescribe calcium pills or calcium-based phosphorus binders.
High blood calcium levels are usually caused by overactive parathyroid glands or consuming too much calcium (either from your diet or calcium-based medications). Your doctor may prescribe certain medications to help suppress PTH or swap your existing medications for some that contain less calcium. Your dietitian can help you figure out which foods to decrease or remove from your diet.
For patients whose PTH levels remain high after trials of medications and diet changes, surgery to remove the parathyroid glands may be necessary.
Most of the phosphorus in your body is stored in your bones and teeth. Phosphorus is found naturally in many different foods such as dairy products, beans, nuts and meats, but is also added to many processed foods. The body likes to keep phosphorus and calcium in balance. When blood phosphorus levels are high, the body pulls calcium levels from your bones into your bloodstream.
Keeping phosphorus levels within target range can help maintain bone health. Your doctor may prescribe phosphate binders to help keep you from absorbing all of the phosphorus from your food. Your dietitian can help you figure out which foods to decrease or remove from your diet.
Healthy kidneys turn vitamin D into an active form called calcitriol. Calcitriol maintains PTH levels and helps the body absorb calcium from food. When the kidneys fail, they stop making calcitriol, making it impossible to absorb calcium from food. Therefore, the body has to take the calcium from your bones instead. When vitamin D levels are low, your doctor may prescribe a pill containing an active form of vitamin D. For patients on dialysis, this medication can be given through an IV during your treatment.
Treatment for Renal Bone Disease
So, how can you keep your bones healthy with kidney disease? Renal osteodystrophy can be managed with a kidney diet, proper medications, and (in the case of kidney failure) dialysis. Treatment involves:
- Restoring the balance between calcium, phosphorus, PTH and vitamin D
- Taking all medications as prescribed by your doctor
- Following the diet advice your dietitian gives you
- Not missing or shortening dialysis treatments
Physical activity is also a great way to help increase your bone strength. Ask your doctor before beginning an exercise regimen. Find a type of exercise most suited to your enjoyment and mobility level.