Sexual Dimorphism in LC-MS/MS-Based Vitamin D Metabolite Profiling and Nutrition-Acquired Biochemical Osteomalacia amongin Adolescents

Shaun Sabico^1*Nasser Al-Daghri¹Amal Alenad¹Yousef Al-Saleh²Malak Nawaz Khattak¹Kaiser Wani¹Abdullah Alnaami¹Jean-Yves Reginster¹Majed S. Alokail¹Etienne Cavalier³

• ¹King Saud University, Riyadh, Saudi Arabia
• ²Healthoasis Hospital, Riyadh, Saudi Arabia
• ³CHU de Liege, Liège, Belgium

We previously reported a high prevalence of biochemical osteomalacia among apparently healthy Arab adolescents using combined mineralization markers. This study examined whether advanced LC-MS/MS–based vitamin D metabolite profiling, including the vitamin D metabolite ratio (VMR), can serve as indicators of biochemical osteomalacia in Arab adolescents. A total of 949 age-and body mass index-matched adolescents (513 girls, mean age 14.9 ± 1.8 years, body mass index, BMI 23.0 ± 5.9; 436 boys, mean age 14.9 ± 1.7 years, BMI 23.7 ± 5.8) were included in this cross-sectional study. Anthropometrics and biochemical parameters [glucose, lipid profile, calcium (Ca), inorganic phosphorus (Pi), alkaline phosphatase (ALP)] were measured using routine assays. Circulating vitamin D metabolites [24,25(OH)₂D (24, 25 VD), VD2, VD3, total VD] were quantified using LC-MS/MS, and VMR calculated as [24,25 VD/VD] × 100. Deficiency cut-offs were: VD <30 nmol/L, 24,25 VD <3.0 nmol/L, VMR <4%. Biochemical osteomalacia was defined as ≥ 2 abnormal markers (low VD, high ALP, low Ca, or low Pi). All vitamin D metabolites were significantly lower in the biochemical osteomalacia group. Overall, VD showed the highest predictive value (AUC 0.71, Youden index 0.40). Stratified analyses revealed VMR as a modest marker in girls (AUC 0.60), while VD3 performed best in boys (AUC 0.77, Youden index 0.60). VD metabolites as a single test are modest predictors of biochemical osteomalacia in adolescents and differ in accuracy according to sex. Findings in this study should be interpreted as exploratory rather than diagnostic, serving to generate hypotheses and lay groundwork for future clinical and public health applications.