Effects of Vitamin D Replacement on Hormones Regulating Iron Metabolism in Individuals With Chronic Kidney Disease

The purpose of the study is to learn more about how treatment with vitamin D can affect iron metabolism and blood levels of two hormones that control iron levels, hepcidin and hemojuvelin in people with chronic kidney disease (CKD). Iron is an essential mineral which is a major component of proteins that carry oxygen in the blood. Problems with iron metabolism can lead to low blood levels (anemia), which can commonly happen in people with CKD. New research over the last decade has uncovered a new hormone called 'hepcidin', which is made in the liver and released into the blood. Hepcidin controls how much iron is in the blood by preventing the absorption of iron from food. Blood levels of hepcidin C are found to be high in people with CKD, and a recent small study in people with normal kidney function showed that treatment with vitamin D decreased hepcidin levels. Another protein, known as 'hemojuvelin', has been recently discovered and is also thought to control the amount of iron in the blood. The relationship between vitamin D and hemojuvelin has never been studied before. In this study, investigators would like to examine the effects of vitamin D on iron metabolism and blood levels of hepcidin C and hemojuvelin in individuals with CKD.