Evidence Supporting the FHH

Since most extra-renal tissues have not been shown to express megalin receptors, it has been suggested that these tissues are more directly impacted by free vitamin D. The inference from studies investigating monocytes that were exposed to increasing doses of 25-OHVD in the presence or absence of VDBP was that monocyte responses to 25-OHVD are attenuated in the presence of VDBP. As more of the free 25-OHVD was bound by VDBP, it was no longer available to act on monocytes. In addition, estimated free 25-OHVD levels were shown to be a better comparison of circulating PTH levels in CKD patients receiving hemodialysis.