Vitamin D Deficiency & Kidney Disorders

Vitamin D is fat-soluble and exists in naturally as vitamin D3. In the skin, it is made under direct sunlight. Vitamin D is also absorbed from food sources that contain vitamin D such as fish, eggs and cod liver oil. Vitamin D is inactive; it has to be processed into an active form. The kidneys are involved in the activation vitamin D; they convert hydroxyvitamin D from the liver to active vitamin D.

The Kidneys

The kidneys have the important job of filtering metabolic wastes and removing excess fluid from the blood. Failure of the kidneys leads to a buildup of metabolic wastes in the body, which can ultimately result in death. The kidneys are also the final step in the activation of vitamin D. They convert hydroxyvitamin D from the liver to active vitamin D that helps in the absorption of calcium in the gut. Failure of the kidneys also affects the activation of inactive vitamin D; this leads to low active vitamin D in the blood. Chronic kidney disease, for example, is a known cause of low active vitamin D in the blood; it's also associated with increased release of parathyroid hormone.

Complications

Any cause of vitamin D deficiency invariably leads to low blood calcium; this is also the case with chronic kidney disease. In chronic kidney disease, there is an increased release of parathyroid hormone. Parathyroid hormone is released from the parathyroid gland, and it causes the breakdown of bone, thereby releasing calcium from bone into the blood. Excessive release of parathyroid hormone leads to weakening of bone, making it more likely to fracture.

Low blood calcium can also cause an irregular pulse; in severe cases, it can cause irreversible heart failure.

.

Related Symptoms

When low blood calcium is severe, it weakens the heart muscle; a weak heart causes shortness of breath while lying down; it also causes leg and belly swelling. Low blood calcium can lead to tetany, or a condition of uncontrollable muscle contractions. Tetany may cause strange sensations over the tongue and lips; it may also cause abnormal twitching of the facial muscles. Calcium is needed to strengthen bone; low blood calcium causes weakening of bone. Excess parathyroid hormone release as a result of low blood calcium worsens an already weak bone. Bone and joint pain are major complaints when parathyroid hormone is in excess. Generalized weakness, abdominal pain, nausea and depression can occur.

Management

A blood test is needed to diagnose vitamin D deficiency. The blood is tested for active vitamin D. A normal level of active vitamin D in the blood should be greater than 30 nanograms per milliliter, or ng/mL; if less than 30 ng/mL, it is abnormal or below normal. An active vitamin D level below 20 ng/mL is defined as vitamin D deficiency.

Treatment

Any disease that leads to vitamin D deficiency should be addressed, and vitamin D must also be supplemented to prevent decrease in bone density and weakening of bone. Supplementation of vitamin D is best done with calcium. The U.S. Department of Health and Human Services recommends the use of vitamin D at doses of 700 to 800 international units, or IUs, with 500 to 1,200 mg of calcium; this is beneficial to bone density. Dietary modifications should include intake of fish, eggs, vitamin D-fortified milk and cod liver oil, which are abundant sources of vitamin D.