WORLD OSTEOPOROSIS DAY
Every Year 20th October is World Osteoporosis Day. This is celebrated every year to increase awareness about osteoporosis which is one of the commonest causes of fractures. Our bones are continuously rebuilding to stay healthy. Bones need:
Calcium and Phosphate: These are used to maintain bones. The kidneys are important in keeping blood levels of calcium and phosphate balanced.
Active Vitamin D (Calcitriol): Healthy kidneys change vitamin D to an active form. This is important to form new bones and to keep blood calcium levels balanced.
Parathyroid hormone (PTH): This is released by the four pea-sized parathyroid glands in your neck to keep calcium levels in your blood stream balanced. When the kidneys are not working properly, this hormone is released to move calcium from your bones into your blood stream.
It is well known that kidneys play a critical role in excretion of water and toxins from the body. However a lesser known fact that kidney plays a critical role in maintaining healthy bone mass and structure by balancing calcium and phosphorus levels in your blood by:
- Activating a form of vitamin D that you get from food and turning it into a form, called calcitriol that your bones can use.
- Removing extra phosphorus from your blood by passing it out in urine.
- Sending phosphate and calcium back into your bloodstream from the kidneys and bones when more is needed.
Several studies have shown that patients with chronic kidney disease (CKD) are at increased risk of bone disease. Mineral and bone disorder in chronic kidney disease (CKD) is a disorder that can affect the bones, heart, and blood vessels of a person with CKD. Mineral and bone disease occurs when kidneys damaged by CKD can’t filter blood and regulate hormones the way they should. Kidney damage from CKD causes mineral and bone disorder because the damaged kidneys do not properly balance the mineral and hormone levels in the body. Damaged kidneys stop:
- Turning vitamin D into calcitriol, creating an imbalance of calcium in your blood.
- Removing excess phosphorus from your blood, triggering your blood to pull calcium out of your bones and causing them to weaken.
Also, when your kidneys are damaged, your parathyroid glands, which are located in your neck but are not related to your thyroid function, release extra PTH into your blood to move calcium from your bones to restore your blood calcium levels; but this response also starves your bones of much-needed calcium. The hormone levels and levels of minerals, such as calcium and phosphorus, then become imbalanced, leading to damage. The complications of mineral and bone disorder include:
- Slowed bone growth and bone deformities.
- Bone fractures.
- Heart and blood vessel problems.
Damaged kidneys must work harder to remove phosphorus from your body. Buildup of phosphorus is associated with less calcium in your blood and with the release of PTH by your parathyroid glands. PTH moves calcium out of your bones and into your blood. The loss of calcium can harm your bones. Bone complications could include (a) slowed bone growth especially if the onset is during childhood leading to short stature that may remain into adulthood (b) another bony deformity that is seen in children sometimes called “renal rickets”, in which the legs bend inward or outward (c) there is increased likelihood of bone fractures in both children as well as adults.
What is alarming is that mineral and bone disorder can not only harm your bones. It can also increase your risk of heart attacks, strokes, and death. This can happen in the following ways: (a) High levels of blood calcium can damage your blood vessels and lead to heart problems. (b)High levels of phosphorus can cause your blood vessels to harden—a process known as calcification. It also causes abnormal hormone regulation, even if your calcium level is acceptable. (c) High levels of PTH and another hormone made in the bones, called FGF23, can also harm both your bones and your heart and blood vessels. Compared with the general population, fracture rates are more than fourfold higher and they are associated with increased risk of prolonged hospitalization in CKD patients and even risk of death. In a recent study from USA, fractures were reported to be greater than two- to 100-fold more common than in age-matched individuals without CKD and death rates after fracture were more than threefold greater for patients with CKD than those without CKD. To add to this health care –associated costs after fracture for patients with CKD exceeded $600 million.
I have also studied the association of bone disease in patients. Nephrotic syndrome common kidney diseases seen in children as well adults. This is one of the few curable kidney diseases if diagnosed and treated promptly. Our study was amongst the first in the world to highlight that children with even simple kidney disease like nephrotic syndrome are at risk of bone disease. This fracture risk persists for many years even after the kidney disease has been cured. The bone disease is due to many factors: the underlying kidney disease as well sometimes the medicines used to treat kidney diseases (steroids and calcineurin inhibitors). The observations in our study have been validated in several other studies, there has been a change in treatment guidelines suggesting shorter courses of steroids and early use of alternatives to steroids in management of nephrotic syndrome. Early diagnosis and appropriate treatment can prevent severe fractures in these patients. Our research paper has highlighted the efficacy of simple interventions like calcium and Vitamin D supplements along with steroids in the prevention of bone diseases in these patients. Also we now have newer modalities to diagnose bone disease like DEXA scan have become widely available and affordable. DEXA is a computerized scan of bones that gives very little radiation and can help in early diagnosis of osteoporosis.
Treatment for mineral and bone disorder aims to control mineral and hormone levels to prevent bone and blood vessel damage. The various strategies that have been used to treat bone disease include:
(a)Dietary changes: eating fewer foods that contain phosphorus is one of the most important steps to help you prevent bone disease and blood vessel calcification. These include eating a low phosphorus diet which includes restriction of dairy products, beverages and preserved foods
(b) A wide array of medicines are now available. These include the following:
- Synthetic calcitriol to reduce PTH levels.
- Calcium supplement and vitamin D.
- Calcimimetics to lower your PTH levels or to treat secondary hyperparathyroidism.
- Phosphate binders, which bind to the phosphorus in food and keep it from being absorbed by your intestines.
- Another development over the last few years newer therapeutic agents like Zolendronic acid and Denusumab to effectively treat osteoporosis.
- Timley initiation of dialysis in patients with stage 5 CKD.
- Preemptive kidney transplant: going for kidney transplant without prior dialysis.
- Rarely a surgery to remove the parathyroid glands that produce hormones may be required
Bone disease in kidney patients is largely preventable. It is related to the severity of kidney disease, the more advanced the kidney disease the more serve the bone diseases. Thus high risk patients should be screened for bone disease including all patients with nephrotic syndrome, chronic kidney disease, and kidney transplant patients who are on prolonged steroids. Thus the time old adage “Prevention is better than Cure” holds very much true for Bone Disease in Kidney patients and you need to preserve and “Save your Kidney function to protect your bones”. For more information on kidney diseases please see my YouTube channel Dr Sanjeev Gulati Kidney Clinic.
(The author is President Elect, India Society of Nephrology, Principal Director Nephrology and Kidney Transplant, Fortis Group of Hospitals, NCR)