Vitamin D deficiency and biochemical variations among urban Saudi adolescent girls according to season

Objectives: To determine seasonal variations in the vitamin D status of Saudi adolescent girls in Riyadh, Kingdom of Saudi Arabia (KSA) and its effect in biochemical and clinical characteristics. Methods: In this prospective study, a total of 2000 Saudi females aged 12-18 years from different schools in Riyadh, KSA participated and submitted a generalized questionnaire with clinical information. Fasting blood samples were obtained in 1618 subjects for the winter season (December to February) and only 499 subjects returned to submit fasting blood samples for the summer season (June-August). Circulating serum 25(OH) D, parathyroid hormone (PTH), and other biomarkers of bone remodeling were measured during both seasons. Results: Vitamin D deficiency (serum 25(OH) D < 25 nmol/L) was significantly higher during summer than winter (63.5% versus 40.8%; p< 0.001). Mean serum PTH was also significantly higher during summer than winter (p< 0.01). In all subjects, serum PTH showed a significant inverse association with 25(OH) D at levels below 40 nmol/L (r=-0.21; p< 0.001). The prevalence of subjects having clinical and metabolic manifestations suggestive of osteomalacia was 2.1% (N=33 out of 1548). Conclusion: Seasonal variations in the vitamin D status of Saudi adolescent females significantly modifies biochemical parameters as response to vitamin D status change. In the meantime, heightened public health awareness should be given to populations at higher risk for vitamin D deficiency.