Serum 25-Hydroxyvitamin D and Intact Parathyroid Hormone as Functional Biomarkers of Bone Mass in Early Childhood
Bibliographic record
Abstract
BACKGROUND: The 25-hydroxyvitamin D (25(OH)D) concentration at which parathyroid hormone (PTH) concentration plateaus has been considered to benchmark vitamin D deficiency. However, in young children, there is limited evidence for a suppression point in the 25(OH)D-PTH relationship or its relevance to bone mass accrual. OBJECTIVES: To determine whether the threshold of 25(OH)D at PTH suppression in young children is corroborated by associations of 25(OH)D (or PTH) with bone mineral content (BMC) and areal bone mineral density (aBMD). METHODS: In a cross-sectional secondary analysis of data from the BONe and mUScle health in Kids (BONUSKids) study of 4-y-old children in Bangladesh, serum 25(OH)D and intact PTH (iPTH) were analyzed by liquid chromatography-tandem mass spectrometry and a chemiluminescent immunoassay, respectively. BMC and aBMD were measured by dual-energy X-ray absorptiometry. Associations between 25(OH)D, iPTH, and bone outcomes (BMC, BMC z-score, aBMD, and aBMD z-score) were modeled using multivariable-adjusted linear regression and spline models. Model fit was compared using Akaike's Information Criteria. RESULTS: Of 534 participants (51% female), 28% had 25(OH)D concentrations <25 nmol/L and 34% had iPTH >6.7 pmol/L. Model fit of the inverse relationship between 25(OH)D and iPTH was optimized with an inflection point at 25 nmol/L [<25 nmol/L: -0.16 pmol/L per 1 nmol/L increase in 25(OH)D; 95% confidence interval (CI): -0.22, -0.10; P < 0.001), above which the slope attenuated (≥25 nmol/L: -0.02 pmol/L; 95% CI: -0.04, -0.003; P = 0.019]. However, the positive linear associations between 25(OH)D and bone mass outcomes were monotonic (P < 0.05), and iPTH was not associated with any bone outcome in adjusted models (P > 0.05 for all). Associations were similar in males and females. CONCLUSIONS: Among 4-y-old children in Dhaka, Bangladesh, we did not identify a 25(OH)D threshold to define vitamin D deficiency based on its association with bone mass. However, efforts to raise 25(OH)D to ≥25 nmol/L may be warranted based on the relatively strong inverse association of 25(OH)D with iPTH below this threshold. This trial was registered at clinicaltrials.gov as #NCT03537443.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".