Reconsidering vitamin D optimal values based on parathyroid hormone levels in a North Algerian cohort: stratification by gender and season.
Level 4 - case-series / case-control
Cross-sectional observational study evaluating biomarker cutoffs
PubMed 35895238 · doi:10.1007/s11657-022-01137-2
What was done
Researchers conducted a cross-sectional study of 451 healthy volunteers aged 19 to 79 years at the University Hospital of Blida, Algeria. Serum 25-hydroxyvitamin D (25(OH)D) was measured using a sequential competitive immuno-fluoroassay. The relationship between 25(OH)D and parathyroid hormone (PTH) was modeled using inverse nonlinear regression on spline plot curves to determine the 25(OH)D threshold at which PTH reaches a plateau, stratified by sex and season.
What was found
The 25(OH)D threshold where PTH stabilized into a virtual plateau was estimated at 25.0 ng/ml in men (PTH plateau at 22.3 pg/ml) and 30.0 ng/ml in women (PTH plateau at 26.8 pg/ml). When stratified by season, the 25(OH)D cutoff was 30.0 ng/ml in warm seasons (PTH plateau at 21.5 pg/ml) and 25.0 ng/ml in cold seasons (PTH plateau at 27.7 pg/ml).
Why it matters
This study provides region-specific physiological thresholds for vitamin D sufficiency in North Africa, suggesting that optimal target values differ by sex and season.
Limits
The cross-sectional design cannot establish causality or determine long-term clinical outcomes such as fracture incidence or bone mineral density. Findings are from a single hospital center. The abstract does not report potential confounders such as dietary calcium intake, renal function, or sun exposure.
Cited by
- supports Parathyroid hormone levels serve as an indirect test to assess vitamin D absorption and severe deficiency.