Environmental factors rather than genetics likely drive vitamin D deficiency in idiopathic scoliosis.

BACKGROUND CONTEXT: Low vitamin D levels in individuals with idiopathic scoliosis (IS) have been reported and suggested as a potential contributor to IS. Bone density has also been shown to be lower in individuals with IS.

PURPOSE: To investigate serum levels of vitamin D, parathyroid hormone (PTH), markers of bone metabolism, and the genetic variation associated with vitamin D levels and bone density in individuals with IS and healthy controls.

STUDY DESIGN/

SETTING

Case-control study combining Scandinavian serum cohorts and genetic cohorts.

PATIENT SAMPLE: Serum analyses: 174 individuals with IS and 153 nonscoliotic controls.

GENETIC ANALYSES: A total of 1,394 individuals with IS and 11,108 controls.

OUTCOME MEASURES: Serum 25-hydroxyvitamin D (25OHD), PTH, C-terminal telopeptide (CTX), osteocalcin, calcium, phosphate, creatinine, albumin, alkaline phosphatase, and leptin. Polygenic risk scores (PRS) for 25OHD and bone mineral density (BMD).

METHODS

Serum samples were analyzed using validated clinical laboratory methods. PRS for 25OHD and BMD were calculated based on previous literature. Statistical analyses were performed using Mann-Whitney U tests, logistic, and linear regression. Mendelian randomization was analyzed using logistic regression and the inverse-variance weighted method.

RESULTS

In the serum cohort, median 25OHD levels were 54.4 nmol/L in individuals with IS and 67.0 nmol/L in controls. Corresponding PTH levels were 4.0 and 3.2 pmol/L. No statistically significant differences were found in CTX, osteocalcin, alkaline phosphatase, or leptin. PRS for 25OHD was associated with serum 25OHD levels. PRS in individuals with IS and controls were nonsignificant for 25OHD, BMD femoral neck, and BMD lumbar spine. A tendency for lower values for estimated BMD heel was seen in individuals with scoliosis compared to controls.

CONCLUSIONS

Our findings indicate altered regulation of the vitamin D-PTH axis in IS, likely driven by environmental rather than genetic factors. Bone turnover markers were comparable between groups; no clear genetically mediated BMD differences could be observed.