I recently started taking vitamin D3 supplements. I decided to do my own research on what this means to the health of my kidneys. Here is my interpretation.
Vitamin D is available through the sun and in a few foods as well. It is actually a hormone. It is processed through the liver and given to the kidneys to be circulated through the blood for optimal health and strong bones. Our parathyroid gland release PTH to help stabilze the situation.
In early kidney failure, the kidney is not able to activate vitamin D. Not only that, but it becomes inefficient at excreting phosphate thus causing this to elevate in blood levels. It can eventually cause bones to become soft and bendable, robbing the body of the vitamin D it needs.
If calcitriol is started early in kidney failure, parathyroid levels may be kept low enough that calcium/phosphorus imbalance never becomes an issue. If it is started later in failure, it is helpful but may not be able to provide as good a response.