Vitamin D Binding Protein Levels in Normal Pre- and Post Menopausal Women

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 257-280-Disorders of Vitamin D Metabolism & Action
Basic/Translational
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-273
Xiangbing Wang*1 and Sue A Shapses2
1Robert Wood Johnson Med School, New Brunswick, NJ, 2Rutgers University, New Brunswick, NJ
Background:  Vitamin D status is typically measured with serum 25-hydroxyvitamin D concentrations, but there are both free and bound forms that may influence the physiological effects of vitamin D.  Vitamin D binding protein (DBP) is the major transport protein for vitamin D metabolites in plasma, where 88-93 % of 25-hydroxyvitamin D (25OHD) is bound to DBP. DBP has been shown to prolong the serum half life of 25OHD in mice, and protect against vitamin D deficiency.  The significance of DBP levels in humans is unclear.  In the present study, we investigate the effects of menopausal status on DBP levels by analyzing levels in normal healthy pre- and post menopausal women.

Subjects and Methods:  Ninety-two female subjects, 45 premenopausal (42 ± 7yo) and 47 post menopausal women (60 ± 5 yo) were enrolled.  Intact parathyroid hormone (iPTH) and Ca levels were determined by our biochemical laboratory.  25OHD levels and DBP levels were determined by radioimmunoassay and an ELISA, respectively.

Results: There are no significant difference in calcium (9.4 ± 0.6 vs 9.5 ± 0.9mg/dl), BMI (29 ± 4 vs 31 ± 5 kg/ m2), 25OHD (26.6 ± 8.7 vs 25.3 ± 6.3 ng/ ml) and iPTH levels (41.8 ± 19.9 vs 39.7 ± 17.6 pg/ml) between pre- and post-menopausal women (P>0.05).  DBP levels were lower in postmenopausal (41.2±16.1 mg/dl) compared to premenopausal women (50.42±22.0 mg/dl, P < 0.01).  DBP levels were inversely correlated with age in these female subjects (r = -0.35, p < 0.05).

Conclusions: DBP levels were lower in postmenopausal women and levels were inversely correlated with age.  It is possible that higher circulating estradiol concentrations up-regulates liver DBP production and are influencing these results, but factors related to aging may have an independent effect.  The physiological significance of lower DBP levels in postmenopausal women requires further investigation.

Nothing to Disclose: XW, SAS

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