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The Free Hormone Hypothesis: Is Free Serum25-Hydroxyvitamin D a Better Marker for Bone Mineral Density in Older Women?

Michaëlsson, Karl ; Rasmusson, Annica ; Wolk, Alicja ; Byberg, Liisa ; Mitchell, Adam LU and Melhus, Håkan (2018) In JBMR Plus 2(6). p.367-374
Abstract
It is presently unclear whether free serum 25 hydroxyvitamin D (S 25(OH)D) better reflects bone health than total S 25(OH)D. We have previously shown that summer total S 25(OH)D values are more useful to predict bone mineral density (BMD) than winter values. Our objective was therefore to compare the relative importance of free and total S 25(OH)D for BMD by season. BMD was measured by dual energy X ray absorptiometry (DXA) in 5002 Swedish women (mean age 68 years) randomly selected from a large population based longitudinal cohort study. Free S 25(OH)D was analyzed by a commercial ELISA and total S 25(OH)D by HPLC–tandem mass spectrometry (MS/MS). Free and total S 25(OH)D co varied with season, with 26% and 29% higher values in August... (More)
It is presently unclear whether free serum 25 hydroxyvitamin D (S 25(OH)D) better reflects bone health than total S 25(OH)D. We have previously shown that summer total S 25(OH)D values are more useful to predict bone mineral density (BMD) than winter values. Our objective was therefore to compare the relative importance of free and total S 25(OH)D for BMD by season. BMD was measured by dual energy X ray absorptiometry (DXA) in 5002 Swedish women (mean age 68 years) randomly selected from a large population based longitudinal cohort study. Free S 25(OH)D was analyzed by a commercial ELISA and total S 25(OH)D by HPLC–tandem mass spectrometry (MS/MS). Free and total S 25(OH)D co varied with season, with 26% and 29% higher values in August compared with those in January–March (nadir). There were no differences in mean BMD between categories of free or total S 25(OH)D in samples collected during winter. Women with higher total S 25(OH)D measured during summer had higher BMD at the total hip. Compared with women who had total S 25(OH)D values above 80 nmol/L during summer, adjusted BMD at the total hip was 6% (95% CI, 1% to 11%) lower for S 25(OH)D concentrations between 30 and 40 mmol/L, and 11% (95% CI, 3% to 19%) lower for those with total S 25(OH)D <30 nmol/L. In contrast, free S 25(OH)D measured during summer was not associated with BMD. Compared with women who had highest free S 25(OH)D measured during summer (>8.8 pmol/L), those with intermediate (2.4–3.5 pmol/L) and lowest (<2.4 pmol/L) free S 25(OH)D during summer did not have lower total hip BMD values (3% [95% CI, −2% to 7%] and −2% [95% CI, −8% to 4%]). In addition, we found no added value for the prediction of BMD with the combined measurement of total and free S 25(OH)D during summer or winter. We conclude that vitamin D status assessed by direct measurements of free S 25(OH)D does not reflect BMD better than total S 25(OH)D. © 2018 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research. (Less)
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publishing date
type
Contribution to journal
publication status
published
in
JBMR Plus
volume
2
issue
6
pages
367 - 374
publisher
Wiley-Blackwell
external identifiers
  • scopus:85068997369
ISSN
2473-4039
DOI
10.1002/jbm4.10059
language
English
LU publication?
no
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4a9daa3d-dd13-4621-8c31-ba4540590f61
date added to LUP
2025-02-07 11:55:08
date last changed
2025-02-08 04:01:56
@article{4a9daa3d-dd13-4621-8c31-ba4540590f61,
  abstract     = {{It is presently unclear whether free serum 25 hydroxyvitamin D (S 25(OH)D) better reflects bone health than total S 25(OH)D. We have previously shown that summer total S 25(OH)D values are more useful to predict bone mineral density (BMD) than winter values. Our objective was therefore to compare the relative importance of free and total S 25(OH)D for BMD by season. BMD was measured by dual energy X ray absorptiometry (DXA) in 5002 Swedish women (mean age 68 years) randomly selected from a large population based longitudinal cohort study. Free S 25(OH)D was analyzed by a commercial ELISA and total S 25(OH)D by HPLC–tandem mass spectrometry (MS/MS). Free and total S 25(OH)D co varied with season, with 26% and 29% higher values in August compared with those in January–March (nadir). There were no differences in mean BMD between categories of free or total S 25(OH)D in samples collected during winter. Women with higher total S 25(OH)D measured during summer had higher BMD at the total hip. Compared with women who had total S 25(OH)D values above 80 nmol/L during summer, adjusted BMD at the total hip was 6% (95% CI, 1% to 11%) lower for S 25(OH)D concentrations between 30 and 40 mmol/L, and 11% (95% CI, 3% to 19%) lower for those with total S 25(OH)D &lt;30 nmol/L. In contrast, free S 25(OH)D measured during summer was not associated with BMD. Compared with women who had highest free S 25(OH)D measured during summer (&gt;8.8 pmol/L), those with intermediate (2.4–3.5 pmol/L) and lowest (&lt;2.4 pmol/L) free S 25(OH)D during summer did not have lower total hip BMD values (3% [95% CI, −2% to 7%] and −2% [95% CI, −8% to 4%]). In addition, we found no added value for the prediction of BMD with the combined measurement of total and free S 25(OH)D during summer or winter. We conclude that vitamin D status assessed by direct measurements of free S 25(OH)D does not reflect BMD better than total S 25(OH)D. © 2018 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.}},
  author       = {{Michaëlsson, Karl and Rasmusson, Annica and Wolk, Alicja and Byberg, Liisa and Mitchell, Adam and Melhus, Håkan}},
  issn         = {{2473-4039}},
  language     = {{eng}},
  number       = {{6}},
  pages        = {{367--374}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{JBMR Plus}},
  title        = {{The Free Hormone Hypothesis: Is Free Serum25-Hydroxyvitamin D a Better Marker for Bone Mineral Density in Older Women?}},
  url          = {{http://dx.doi.org/10.1002/jbm4.10059}},
  doi          = {{10.1002/jbm4.10059}},
  volume       = {{2}},
  year         = {{2018}},
}