Vitamin D and bone health in psoriatic arthritis: bone mineral density, turnover markers, and biochemical measures.

BACKGROUND: Psoriatic arthritis (PsA) is an autoimmune disease that often leads to joint inflammation and bone changes, including osteoporosis. The role of vitamin D in bone health is well documented, but its effects in PsA, particularly regarding bone mineral density (BMD), trabecular bone score (TBS), and bone turnover markers (BTM), remain unclear. This study aimed to evaluate the relationship between vitamin D status and these bone parameters in PsA patients. MATERIALS AND METHODS: A cross-sectional study was conducted with 68 patients diagnosed with PsA. Participants were divided into two groups based on their 25(OH)D3 concentrations (< 75 nmol/L and > 75 nmol/L). Patients' BMD and TBS were measured using dual-energy X‑ray absorptiometry (DXA), while serum samples were analyzed for calcium, phosphorus, osteocalcin, CTX‑I, and parathyroid hormone (PTH) concentrations. RESULTS: Patients with 25(OH)D3 levels > 75 nmol/L showed significantly lower BMD at the lumbar spine compared to those with levels < 75 nmol/L (P = 0.020). Significant differences were observed in BTM, with higher concentrations of osteocalcin and CTX‑I in patients with 25(OH)D3 levels > 75 nmol/L. No significant differences were found for TBS, alkaline phosphatase, or other biochemical parameters. CONCLUSION: Our findings indicate potential differences in lumbar spine BMD and bone turnover markers across vitamin D levels in PsA patients. The findings highlight the complexity of bone metabolism in PsA and suggest that vitamin D supplementation may have a nuanced impact on bone health. Further studies with larger cohorts are needed to confirm these results and explore their clinical implications.