The kidneys play several different roles in the body. They filter blood to regulate its mineral and water content, and in the process make urine. Kidneys help synthesize vitamin D, regulate blood pressure and signal the bone marrow to make red blood cells. Therefore, the chemicals found in blood, such as creatinine and the chemicals synthesized by the kidneys such as vitamin D vary in concentration, depending on kidney function.
Creatinine and Kidney Function
According to "Lehninger Principles of Biochemistry," by Dr. Albert Lehninger and others, muscles and the cells of other tissues store and release energy in order to perform work. This energy is stored and released in the chemical ATP. Creatine helps regenerate ATP after it has been used. Creatinine is the breakdown product of creatine. It is released into the blood and filtered by the kidneys. When kidney function declines, the kidneys are unable to transfer the creatinine to the urine and levels in the body rise. The creatinine itself has no known negative effects on the body, but serves as a marker of kidney function.
Vitamin D and Kidney Function
Vitamin D is made by a number of reactions in the body. As noted by "Robbins and Cotran Pathologic Basis of Disease" by Dr. Vinay Kumar, a chemical derived from cholesterol is made into a form of vitamin D, called vitamin D-3, in the skin by a reaction catalyzed by sunlight. This form travels to the liver, which converts it into the second form of vitamin D, called calcidiol. Calcidiol then goes to the kidneys to be converted to the highly active form of vitamin D called calcitriol. Without kidney function, this form of vitamin D is not synthesized and vitamin D levels decline.
Consequences of Declining Kidney Function
With declining kidney function, creatinine rises, indicating the state of the kidneys, and can be used as a marker for starting dialysis, which is the artificial filtering of blood by a machine. Without therapy, the kidney becomes dysfunctional. Low vitamin D affects calcium levels in the body and the bones. Without vitamin D, the levels of calcium in the body drops. This has negative effects on nerves and muscles, making them prone to contract too forcefully and frequently, and the nerves will have trouble communicating. In order to restore the calcium balance, the bones release calcium into the blood, making them brittle.
Risk Factors/Causes
High blood pressure and diabetes pose major risk factors for a decline in kidney function. Hereditary and environmental causes and other diseases such as infections can also contribute to a decline in kidney function.
Diagnosis
Changes in urine output, shortness of breath, fluid buildup in the legs or swelling in the body and fatigue are all symptoms of kidney disease, but not specific to it. Studies of blood and urine help to establish kidney problems. Imaging such as X-rays, CT scan or MRI scans may also be useful. A kidney biopsy, in which a small piece of tissue is removed for study can also help to establish a diagnosis.
Treatment
High creatinine in the context of a decline in kidney function does not have to be treated because it is not inherently dangerous, but since it is indicative of decreased kidney function, it signals the need for therapy. The treatment will depend on the underlying cause. Risk factors such as high blood pressure and diabetes need to be kept under control. If the cause is an overly active immune system, a number of drugs such as corticosteroids can decrease the immune response. Low vitamin D levels can be supplemented. Complete kidney failure can be treated with dialysis and, if warranted, a kidney transplant.
References
- "Lehninger Principles of Biochemistry"; Albert Lehninger, David L. Nelson, and Michael M. Cox; 5th Ed 2008
- "Robbins & Cotran Pathologic Basis of Disease"; Vinay Kumar, Abul K. Abbas, Nelson Fausto, Jon Aster; 8th Ed 2009
