Bio-available Vitamin D is reduced by half during pregnancy – Jan 2017

Clinical Utility of Measurement of Vitamin D-Binding Protein and Calculation of Bioavailable Vitamin D in Assessment of Vitamin D Status.

Ann Lab Med. 2017 Jan;37(1):34-38. doi: 10.3343/alm.2017.37.1.34.
Kim HJ1, Ji M2, Song J3, Moon HW4, Hur M4, Yun YM5.

VitaminDWiki

Vitamin D Binding Protein is just one of 4 genes not visible to standard Vitamin D tests
Bio-available calculation does not notice the affect of CYP27B1, CYP24A1, and VDR
The active D actually getting to the cells is a function of measured D and all 4 genes

Genetics category listing contains the following

331 articles in the Genetics category

see also

Vitamin D blood test misses a lot
in Visio for 2023

  • Vitamin D from coming from tissues (vs blood) was speculated to be 50% in 2014, and by 2017 was speculated to be 90%
  • Note: Good blood test results (> 40 ng) does not mean that a good amount of Vitamin D actually gets to cells
  • A Vitamin D test in cells rather than blood was feasible (2017 personal communication)
  •    Commercially available 2019
    • However, test results would vary in each tissue due to multiple genes
  • Good clues that Vitamin D is being restricted from getting to the cells
    1) A vitamin D-related health problem runs in the family
    2) Slightly increasing Vitamin D shows benefits (even if conventional Vitamin D test shows an increase)
    3) Vitamin D Receptor test (<$30) scores are difficult to understand in 2016
    • easier to understand the VDR 23andMe test results analyzed by FoundMyFitness in 2018

    4) Back Pain


Note: Vitamin D Binding Protein = GC


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BACKGROUND:
The associations of vitamin D deficiency with various clinical conditions highlighted the importance of vitamin D testing. Currently, clinicians measure only the total 25-hydroxyvitamin D [25(OH)D] concentration, regardless of its bioavailability. We aimed to determine the effect of vitamin D-binding protein (VDBP) on 25(OH)D bioavailability.
METHODS:
Serum samples were collected from 60 healthy controls, 50 pregnant women, and 50 patients in intensive care units (ICUs). Total 25(OH)D was quantified by liquid chromatography with tandem mass spectrometry, and VDBP levels were determined by using an ELISA kit (R&D Systems, USA). The bioavailable 25(OH)D levels were calculated by using total 25(OH)D, VDBP, and albumin concentrations.
RESULTS:
In comparison with healthy controls, the total 25(OH)D concentration was significantly lower in ICU patients (median, 11.65 vs 18.25 ng/mL; P<0.00001), but no significant difference was noted between pregnant women (18.25 ng/mL) and healthy controls. The VDBP level was significantly lower in ICU patients (95.58 vs 167.18 μg/mL, P=0.0002) and higher in pregnant women (225.01 vs 167.18 μg/mL, P=0.008) compared with healthy controls. Nonetheless, the calculated bioavailable 25(OH)D levels of ICU patients and pregnant women were significantly lower than those of healthy controls (1.97 and 1.93 ng/mL vs 2.56 ng/mL; P=0.0073 and 0.0027).
CONCLUSIONS:
A single marker of the total 25(OH)D level is not sufficient to accurately evaluate vitamin D status, especially in pregnant women. In cases where VDBP concentrations may be altered, VDBP measurements and bioavailable 25(OH)D calculations may help to determine vitamin D status accurately.

PMID: 27834063 DOI: 10.3343/alm.2017.37.1.34


Fig. 2. Comparison of total 25-hydroxyvitamin D [25(OH)D], vitamin D-binding protein (VDBP), and calculated bioavailable 25(OH)D by gestational stage.

Image

  • (A) Total 25(OH)D levels were not significantly different between the 1st and 2nd and 3rd trimesters (median, interquartile range: 1st trimester: 18.20, 15.07-23.87 ng/mL; 2nd and 3rd trimesters: 18.30, 13.75-25.70 ng/mL).
  • (B) VDBP levels during the 2nd and 3rd trimesters were significantly higher than those during the 1st trimester (1st trimester: 102.20, 84.75-259.90 µg/mL, 2nd and 3rd trimesters: 273.65, 163.75-453.98 µg/mL).
  • (C) The calculated bioavailable 25(OH)D level in the 2nd and 3rd trimesters was significantly lower than that in the 1st trimester (1st trimester: 4.19, 2.09-5.67 ng/mL; 2nd and 3rd trimesters, 1.73, 0.90-2.43 ng/mL).
  • P values were calculated by the Mann-Whitney test.
  • Two dashed lines denote vitamin D deficiency and severe vitamin D deficiency.
  • The arrowheads and dots represent the outside value (>1.5× interquartile ranges) and far-out value (>3× interquartile ranges), respectively.
  • The horizontal lines represent the maximum and minimum values, except for the outside value and far-out value.

Fig. 1. Comparison of total 25-hydroxyvitamin D [25(OH)D], vitamin D binding protein (VDBP), and calculated bioavailable 25(OH)D in the three study groups.

Image

  • (A) The total 25(OH)D level in intensive care unit (ICU) patients (median, interquartile range: 11.65, 7.86-14.87 ng/mL) was significantly lower than that in healthy controls (18.25, 13.48-23.78 ng/mL) or in pregnant women (18.25, 13.98-25.24 ng/mL).
  • (B) The VDBP level in
    pregnant women (225.01, 130.24-422.92 μg/mL) was significantly higher, and the
    VDBP level in ICU patients (95.58, 61.15-167.34 μg/mL) was significantly lower
    than that in healthy controls (167.18, 105.99-257.70 μg/mL). (
  • C) The calculated bioavailable 25(OH)D levels of
    ICU patients (1.97, 1.48-3.15 ng/mL) and
    pregnant women (1.93, 1.03-3.41 ng/mL) were significantly lower than those in
    healthy controls (2.56, 1.95-4.22 ng/mL).
  • P values were calculated by the Mann-Whitney test.
  • Two dashed lines denote vitamin D deficiency and severe vitamin D deficiency.
  • The arrowheads and dots represent the outside value (>1.5? interquartile ranges) and far-out value (>3? interquartile ranges), respectively.
  • The horizontal lines represent maximum and minimum values, except for the outside value and far-out value.

Equations

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