Bone Abstracts

Background: Vitamin D status is associated with bone health. Vitamin D deficiency leads to decreased bone formation and increased bone resorption. 25-hydroxyvitamin D (25(OH) D), parathyroid hormone (PTH) levels in children could affect bone turnover, and in turn, the bone markers should reflect vitamin D condition. In children the relationships among 25(OH) D, PTH and bone turnover markers are remain.

Objective: To explore the associations among serum 25(OH) D, intact-parathyroid hormone (iPTH) and bone turnover markers in Chinese children; to observe the changes of serum 25(OH) D, iPTH and bone turnover markers along with age.

Methods: Data were collected during summer December, 2012 and March, 2013 in 85 boys and 65 girls who came to Division of Nutrition, Growth and Development & Endocrinology of Department of Pediatrics, Second Hospital of Hebei Medical University for health examine. Measurements included serum 25(OH) D, iPTH, osteocalcin (OC), alkalinephosphatease (ALP), bone alkalinephosphateasecollagen (BAP), calcium (Ca), phosphorus (P) and urine deoxypyridinoline (DPD), urine creatinine (Cr) and dietary intake of vitamin D and calcium, sunlight exposure, height, weight and BMI.

Results: i) According to serum 25(OH) D levels, children were divided into four groups like <27.5 nmol/l, 27.5–50 nmol/l, 50–75 nmol/l and >75 nmol/l groups. We found serum OC levels decreased along with the increased 25(OH) D levels. All the subjects were grouped based on serum iPTH levels as <1 pmol/l, 1–1.5 pmol/l, 1.5–2 pmol/l and >2 pmol/l. We found OC and BAP levels increased obviously along with the increased iPTH levels. ii) The relevancies between 25(OH) D, iPTH and bone metabolism markers were analyzed by spearman correlation test. Serum OC was negatively related to 25(OH) D (R=−0.445, P<0.001) and positively related to iPTH (R=0.242, P=0.003). Serum BAP and ALP were both positively related to iPTH (R=0.3, P<0.001; R=0.291, P<0.001). There was obviously positive relation between serum ALP and BAP of children either in different age or different gender. There were no obvious relations among other markers. iii) The urine-DPD levels were higher in infants & toddlers than school age & adolescents; serum OC levels were higher in school age & adolescents than infants & toddlers.

Conclusion: i) Serum 25(OH) D and iPTH are closely related to bone turnover markers, however it is not clear whether to assess the suitable 25(OH) D level by bone turnover markers. ii) Serum 25(OH) D and bone turnover markers were different in different ages in Chinese children.

Disclosure: The authors declared no competing interests.