title: The serum level of 25-hydroxyvitamin D for maximal suppression of parathyroid hormone in children: the relationship between 25-hydroxyvitamin D and parathyroid hormone.
abstract: OBJECTIVE
  Serum level of 25-hydroxyvitamin D (25-OHD) is considered as the most appropriate marker of vitamin D status. However, only a few studies have investigated the relationship between 25-OHD and parathyroid hormone (PTH) in children. To this end, this study was aimed at evaluating the lowest 25-OHD level that suppresses the production of parathyroid hormone in children.
  
  
  METHODS
  A retrospective record review was performed for children aged 0.2 to 18 years (n=193; 106 boys and 87 girls) who underwent simultaneous measurements of serum 25-OHD and PTH levels between January 2010 and June 2014.
  
  
  RESULTS
  The inflection point of serum 25-OHD level for maximal suppression of PTH was at 18.0 ng/mL (95% confidence interval, 14.3-21.7 ng/mL). The median PTH level of the children with 25-OHD levels of <18.0 ng/mL was higher than that of children with 25-OHD levels ≥ 18.0 ng/mL (P<0.0001). The median calcium level of children with 25-OHD levels<18.0 ng/mL was lower than that of children with 25-OHD levels≥18.0 ng/mL (P=0.0001). The frequency of hyperparathyroidism was higher in the children with 25-OHD levels<18.0 ng/mL than in the children with 25-OHD levels≥18.0 ng/mL (P<0.0001). Hypocalcemia was more prevalent in the children with 25-OHD levels<18.0 ng/mL than in the children with 25-OHD levels≥18.0 ng/mL (P<0.0001).
  
  
  CONCLUSIONS
  These data suggest that a vitamin D level of 18.0 ng/mL could be the criterion for 25-OHD deficiency in children at the inflection point of the maximal suppression of PTH.
authors.affiliation: Department of Pediatrics, Ewha Womans University School of Medicine, Seoul, Korea.
authors.forename: Jung In
authors.initials: JI
authors.lastname: Kang
authors.affiliation: Department of Pediatrics, Ewha Womans University School of Medicine, Seoul, Korea.
authors.forename: Yoon Suk
authors.initials: YS
authors.lastname: Lee
authors.affiliation: Department of Pediatrics, Ewha Womans University School of Medicine, Seoul, Korea.
authors.forename: Ye Jin
authors.initials: YJ
authors.lastname: Han
authors.affiliation: Clinical Trial Center, Ewha Womans University Medical Center, Seoul, Korea.
authors.forename: Kyoung Ae
authors.initials: KA
authors.lastname: Kong
authors.affiliation: Department of Pediatrics, Ewha Womans University School of Medicine, Seoul, Korea.
authors.forename: Hae Soon
authors.initials: HS
authors.lastname: Kim
keywords: Parathyroid hormone; Vitamin D; Vitamin D deficiency