Seasonal vitamin D and bone metabolism in women of reproductive age in urban Beijing.

BACKGROUND AND OBJECTIVES This study aimed to evaluate the relationship between serum 25-hydroxy-vitamin D and bone metabolism in healthy women of reproductive age. METHODS AND STUDY DESIGN This study included 100 healthy female residents of Beijing (23-30 years old), who underwent bone ultrasonography as well as testing to evaluate serum25-hydroxy-vitamin D, parathyroid hormone, bone alkaline phosphatase, calcium, sodium, phosphorus, and alkaline phosphatase. RESULTS Mean 25-hydroxy-vitamin D in the winter (22.3±3.55 nmol/L) was significantly lower than that in the summer (46.2±16.3 nmol/L). In the winter, a negative correlation was observed between 25-hydroxy-vitamin D and parathyroid hormone(r=0.300, p=0.002) and bone alkaline phosphatase (r=0.274, p=0.016). In the summer, a negative correlation was observed between 25-hydroxy-vitamin D and parathyroid hormone (r=0.386, p<0.001) and bone alkaline phosphatase (r=0.523, p<0.001). Serum calcium, sodium, phosphorus, and alkaline phosphatase were within the normal ranges for both winter and summer, and exhibited no significant correlations with serum 25-hydroxy-vitamin D. The mean speed of sound during bone ultrasonography was 4,125±365 m/s, and a linear correlation was observed between 25-hydroxy-vitamin D and the speed of sound (r=0.215, p=0.031). Serum alkaline phosphatise was not correlated with bone alkaline phosphatase. CONCLUSION Serum vitamin D deficiency was common among healthy women of childbearing age in Beijing during both winter and summer. Furthermore, bone ultrasonography findings and serum vitamin D, parathyroid hormone, and bone alkaline phosphatase accurately reflected these women's bone metabolism status.