Kidneys are certainly among the most important organs with regard to the metabolism of the vitamin D endocrine system. It is known that 1,25 (OH)2 vitamin D (or calcitriol) – the system’s most active metabolite in terms of function – is indeed produced within kidney tissue, where cytochrome CYP27B1 is maximally expressed. This gene is responsible for synthesizing the 1-alpha-hydroxylase enzyme, which is able to convert 25 (OH) vitamin D – which mostly comes from the liver – into calcitriol. Calcitriol is the most powerful stimulator of the vitamin D receptor (VDR), whose activity generates the most important functions of this hormonal system within the human body.
