Trial reportThe Journal of clinical endocrinology and metabolism2015
Free 25(OH)D and Calcium Absorption, PTH, and Markers of Bone Turnover.
Trial report in The Journal of clinical endocrinology and metabolism, 2015. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 37 papers.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
37 citing papers in PubMed, 59 citations in OpenAlex.
- Assessment of the effect of routine-dose vitamin D3 supplementation in Chinese women of childbearing age with vitamin D insufficiency.European journal of nutrition · 2025Trial
- Total, Bioavailable, and Free 25(OH)D Relationship with Indices of Bone Health in Elderly: A Randomized Controlled Trial.The Journal of clinical endocrinology and metabolism · 2021Trial
- Assessing the impact of a mushroom-derived food ingredient on vitamin D levels in healthy volunteers.Journal of the International Society of Sports Nutrition · 2020Trial
- Trial
- Associations Between Change in Total and Free 25-Hydroxyvitamin D With 24,25-Dihydroxyvitamin D and Parathyroid Hormone.The Journal of clinical endocrinology and metabolism · 2018Trial
- The relationship of Physical performance and Osteoporosis prevention with vitamin D in older African Americans (PODA).Contemporary clinical trials · 2018Trial
- Racial differences in calculated bioavailable vitamin D with vitamin D/calcium supplementation.AIDS (London, England) · 2017Trial
- Effects of Cholecalciferol vs Calcifediol on Total and Free 25-Hydroxyvitamin D and Parathyroid Hormone.The Journal of clinical endocrinology and metabolism · 2017Trial
- Effects of High-Dose Vitamin D2 Versus D3 on Total and Free 25-Hydroxyvitamin D and Markers of Calcium Balance.The Journal of clinical endocrinology and metabolism · 2016Trial
- Vitamin D status of black and white Americans and changes in vitamin D metabolites after varied doses of vitamin D supplementation.The American journal of clinical nutrition · 2016Trial
- Effects of vitamin D binding protein phenotypes and vitamin D supplementation on serum total 25(OH)D and directly measured free 25(OH)D.European journal of endocrinology · 2016Trial
- Investigating the interrelationship of vitamin K and vitamin D status on bone density: results from the VITamin D and OmegA-3 TriaL.JBMR plus · 2026Article
- Safety and Efficacy of Loading Doses of Vitamin D: Recommendations for Effective Repletion.Pharmaceuticals (Basel, Switzerland) · 2024Article
- Circulating total 25(OH)D and calculated free 25(OH)D in professional academy footballers at a northerly latitude in the UK.Biology of sport · 2024Article
- Scientific opinion on the tolerable upper intake level for vitamin D, including the derivation of a conversion factor for calcidiol monohydrate.EFSA journal. European Food Safety Authority · 2023Article
- Free and bioavailable 25-hydroxyvitamin D thresholds for bone metabolism and their associations with metabolic syndrome in Chinese women of childbearing age.Frontiers in nutrition · 2023Article
- Vitamin D and the Kidney: Two Players, One Console.International journal of molecular sciences · 2022Review
- Absence of causal association between Vitamin D and bone mineral density across the lifespan: a Mendelian randomization study.Scientific reports · 2022Article
- 100 YEARS OF VITAMIN D: Combined hormonal contraceptives and vitamin D metabolism in adolescent girls.Endocrine connections · 2022Article
- Different threshold levels of circulating total and free 25-hydroxyvitamin D for the diagnosis of vitamin D deficiency in obese adolescents.European journal of pediatrics · 2021Article
Corrections and comments
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Authors and funding
8 authors at 1 institution in 1 country.
Funding
Abstract
contextIt has been proposed that serum free 25-hydroxyvitamin D [25(OH)D] may better reflect vitamin D action than total 25(OH)D. An ELISA for serum free 25(OH)D has recently become available, permitting direct assay.
objectiveTo determine whether serum free 25(OH)D provides additional information in relation to calcium absorption and other biomarkers of vitamin D action compared to total serum 25(OH)D.
settingAmbulatory research setting in a teaching hospital. OUTCOME: Serum free 25(OH)D measured in a previously performed study of varied doses of vitamin D3 (placebo and 800, 2000, and 4000 IU) on calcium absorption, PTH, procollagen type 1 N-terminal propeptide, and C-terminal telopeptides of type I collagen. Free 25(OH)D was measured by ELISA. Calcium absorption was measured at baseline and at 10 weeks using stable dual calcium isotopes.
resultsSeventy-one subjects completed this randomized, placebo-controlled trial. Baseline group mean free and total 25(OH)D varied from 4.7 ± 1.8 to 5.4 ± 1.5 pg/mL, and from 23.7 ± 5.9 to 25.9 ± 6.1 ng/mL, respectively. Participants assigned to the 4000-IU dose arm achieved free 25(OH)D levels of 10.4 pg/mL and total 25(OH)D levels of 40.4 ng/mL. Total and free 25(OH)D were highly correlated at baseline and after increasing vitamin D dosing (r = 0.80 and 0.85, respectively). Free 25(OH)D closely reflected changes in total 25(OH)D. PTH was similarly correlated at baseline and follow-up with total and free 25(OH)D. Serum C-terminal telopeptides of type I collagen had a moderate positive correlation with total and free 25(OH)D at follow-up. The serum 1,25-dihydroxyvitamin D change increased significantly with the change in 25(OH)D but not with the change in free 25(OH)D.
conclusionThere was no advantage from measuring free over total 25(OH)D in assessing the response of calcium absorption, PTH, and markers of bone turnover to vitamin D. Free 25(OH)D responded to increasing doses of vitamin D in a similar fashion to total 25(OH)D.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.