Bone Abstracts

Vitamin D and its metabolites are bound to vitamin D binding protein (DBP) in the circulation. Only a small proportion is in unbound, free form. According to the ‘free-hormone-hypothesis’ only the free form is biologically active. DBP is a polymorphic protein and different variants of the protein differ in their ability to bind vitamin D. This may have an impact on the amount of free and bioavailable (free+albumin-bound) 25-hydroxyvitamin D (25(OH)D) in the circulati...