Increased Plasma Concentrations of Vitamin D Metabolites and Vitamin D Binding Protein in Women Using Hormonal Contraceptives: A Cross-Sectional Study
Nutrients 2013, 5(9), 3470-3480; doi:10.3390/nu5093470
Ulla K. Møller 1, kristine.moller@ki.au.dk, Susanna við Streym 1, Lars T. Jensen 2, Leif Mosekilde 1, Inez Schoenmakers 3, Shailja Nigdikar 3 and Lars Rejnmark 1
1 Department of Endocrinology and Internal Medicine, THG, Aarhus University Hospital, Tage Hansens Gade
2, DK, Aarhus 8000, Denmark 2 Department of Clinical Physiology, Glostrup University Hospital, Copenhagen DK-2900, Denmark
3 MRC Human Nutrition Research, Cambridge CB1 9NL, UK
(This article belongs to the Special Issue Vitamin D and Human Health)
Use of hormonal contraceptives (HC) may influence total plasma concentrations of vitamin D metabolites. A likely cause is an increased synthesis of vitamin D binding protein (VDBP). Discrepant results are reported on whether the use of HC affects free concentrations of vitamin D metabolites.
Aim: In a cross-sectional study, plasma concentrations of vitamin D metabolites, VDBP, and the calculated free vitamin D index in users and non-users of HC were compared and markers of calcium and bone metabolism investigated.
Results: 75 Caucasian women aged 25–35 years were included during winter season. Compared with non-users (n = 23), users of HC (n = 52) had significantly higher plasma concentrations of 25-hydroxyvitamin D (25OHD) (median 84 interquartile range: [67–111] vs. 70 [47–83] nmol/L, p = 0.01), 1,25-dihydroxyvitamin D (1,25(OH)2D) (198 [163–241] vs. 158 [123–183] pmol/L, p = 0.01) and VDBP (358 [260–432] vs. 271 [179–302] µg/mL, p < 0.001). However, the calculated free indices (FI-25OHD and FI-1,25(OH)2D) were not significantly different between groups (p > 0.10). There were no significant differences in indices of calcium homeostasis (plasma concentrations of calcium, parathyroid hormone, and calcitonin, p > 0.21) or bone metabolism (plasma bone specific alkaline phosphatase, osteocalcin, and urinary NTX/creatinine ratio) between groups.
In conclusion: Use of HC is associated with 13%–25% higher concentrations of total vitamin D metabolites and VDBP. This however is not reflected in indices of calcium or bone metabolism. Use of HC should be considered in the interpretation of plasma concentrations vitamin D metabolites.
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Contention: Increase vs decrease