Association of low 25-hydroxyvitamin D concentrations with elevated parathyroid hormone concentrations and low cortical bone density in early pubertal and prepubertal

Background: Very few studies have evaluated both parathyroid hormone (PTH) and 25-hydroxyvitamin D [25(OH)D] and their effects on bone mass in children. Objective: We studied the associations of serum 25(OH)D and intact PTH (iPTH) with bone mineral content (BMC) and bone mineral density (BMD) at different bone sites and the relation between serum 25(OH)D and iPTH in early pubertal and prepubertal Finnish girls. Design: The subjects were 10-12-y-old girls (n = 193) at Tanner stage 1 or 2, who reported a mean (plus or minus SD) dietary calcium intake of 733 plus or minus 288 mg/d. 25(OH)D, iPTH, tartrate-resistant acid phosphatase 5b (TRAP 5b), urinary calcium excretion, BMC, areal BMD, and volumetric BMD were assessed by using different methods. Results: Thirty-two percent of the girls were vitamin D deficient [serum 25(OH)D 25 nmol/L], and 46% of the girls had an insufficient concentration (26-40 nmol/L). iPTH and TRAP 5b concentrations were significantly higher in the deficient group than in the insufficient and sufficient groups [iPTH: 43.9 plus or minus 15.7 compared with 38.6 plus or minus 11.2 pg/L (P = 0.049) and 32.7 plus or minus 12.1 pg/L (P < 0.001), respectively; TRAP 5b: 12.2 plus or minus 2.9 compared with 11.0 plus or minus 2.8 U/L (P = 0.009) and 10.9 plus or minus 1.9 U/L (P = 0.006), respectively]. The girls in the deficient group also had significantly lower cortical volumetric BMD of the distal radius (P < 0.001) and tibia shaft (P = 0.002). High iPTH concentrations were also associated with low total-body apparent mineral density and urinary calcium excretion (P < 0.007). Conclusions: Vitamin D-deficient girls have low cortical BMD and high iPTH concentrations, which are consistent with secondary hyperparathyroidism. A low vitamin D concentration accompanied by high bone resorption (TRAP 5b) may limit the accretion of bone mass in young girls.