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Vitamin D Binding Protein masks how much Vitamin D gets to tissues – May 2019

Vitamin D Binding Protein, Total and Free Vitamin D Levels in Different Physiological and Pathophysiological Conditions.

Front Endocrinol (Lausanne). 2019 May 28;10:317. doi: 10.3389/fendo.2019.00317
Bikle DD1,2, Schwartz J1.
1 Department of Medicine, University of California, San Francisco, San Francisco, CA, United States.
2 Endocrine Research Unit, San Francisco Veterans Affairs Medical Center, San Francisco, CA, United States.

Vitamin D Binding Protein category listing has 166 items and the following introduction

Vitamin D Binding Protein (GC) gene can decrease the bio-available Vitamin D that can get to cells,

VDBP is NOT directly detected by vitamin D blood tests
Blood Test Misses a lot (VDW 3439)
MS and Vitamin D Binding Protein:

TB and Vitamin D Binding Protein:

Breathing and Vitamin D Binding Protein:

Infant-Child and Vitamin D Binding Protein:

 Download the PDF from VitaminDWiki

Free Vitamin D (pg/ml) varies


This review focuses on the biologic importance of the vitamin D binding protein (DBP) with emphasis on its regulation of total and free vitamin D metabolite levels in various clinical conditions. Nearly all DBP is produced in the liver, where its regulation is influenced by estrogen, glucocorticoids and inflammatory cytokines but not by vitamin D itself. DBP is the most polymorphic protein known, and different DBP alleles can have substantial impact on its biologic functions. The three most common alleles-Gc1f, Gc1s, Gc2-differ in their affinity with the vitamin D metabolites and have been variably associated with a number of clinical conditions. Although DBP has a number of biologic functions independent of vitamin D, its major biologic function is that of regulating circulating free and total levels of vitamin D metabolites. 25 hydroxyvitamin D (25(OH)D) is the best studied form of vitamin D as it provides the best measure of vitamin D status. In a normal non-pregnant individual, approximately 0.03% of 25(OH)D is free; 85% is bound to DBP, 15% is bound to albumin.
The free hormone hypothesis postulates that only free 25(OH)D can enter cells.
This hypothesis is supported by the observation that mice lacking DBP, and therefore with essentially undetectable 25(OH)D levels, do not show signs of vitamin D deficiency unless put on a vitamin D deficient diet.

Similar observations have recently been described in a family with a DBP mutation.
This hypothesis also applies to other protein bound lipophilic hormones including glucocorticoids, sex steroids, and thyroid hormone. However, tissues expressing the megalin/cubilin complex, such as the kidney, have the capability of taking up 25(OH)D still bound to DBP, but most tissues rely on the free level.
Attempts to calculate the free level using affinity constants generated in a normal individual along with measurement of DBP and total 25(OH)D have not accurately reflected directly measured free levels in a number of clinical conditions. In this review, we examine the impact of different clinical conditions as well as different DBP alleles on the relationship between total and free 25(OH)D, using only data in which the free 25(OH)D level was directly measured. The major conclusion is that a number of clinical conditions alter this relationship, raising the question whether measuring just total 25(OH)D might be misleading regarding the assessment of vitamin D status, and such assessment might be improved by measuring free 25(OH)D instead of or in addition to total 25(OH)D.

Created by admin. Last Modification: Wednesday June 19, 2019 16:31:47 GMT-0000 by admin. (Version 9)

Attached files

ID Name Comment Uploaded Size Downloads
12160 VDBP peaks.jpg admin 19 Jun, 2019 15:46 19.47 Kb 355
12159 VDBP Bickle.pdf PDF 2019 admin 19 Jun, 2019 15:45 369.89 Kb 484
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