title: [Study on the activity of serum bone alkaline phosphatase and its relations to the heritability among pre-puberty twins].
abstract: OBJECTIVE
  To evaluate calcium deficiency and demand in pre-puberty twins and to analyze the heritability of serum bone alkaline phosphatase (BALP).
  
  
  METHODS
  A total of 73 pairs of twins aged 9-16 years were examined by BALP test. Microsatellite polymorphism was used to diagnose the zygosity of twins, while both intraclass correlation coefficient method and Christian formula were performed to investigate heritability of serum BALP.
  
  
  RESULTS
  The results of zygosity diagnosis displayed that 34 pairs of twins were monozygotic (MZ) twins and 39 pairs were dizygotic (DZ) twins. 97.9% of the subjects appeared unusual in the activity of BALP, with activity of BALP > 250 U/L in 43.1% of subjects and 200-250 U/L in 54.8% of the subjects. The intake of calcium was unsatisfied in 48.4% of the boys and 39.0% in girls. Less than 10.0% of the subjects were satisfied with the intake of calcium in each age group while over 45.0% of the subjects in 10-13 age group were deficient in calcium. Differences between the means of BALP in different sex groups (t = 1.633, P = 0.105) and different age groups (F = 0.323, P = 0.924) were not statistically significant. Heritability analysis displayed that intra-class variation, inter-class variation, intra-class correlation coefficient were 191.54, 1462.22, 0.77 in MZ twins, and those were 491.03, 1475.57, 0.50 in DZ twins respectively with the heritability of BALP activity as 0.54.
  
  
  CONCLUSIONS
  Calcium deficiency is commonplace in pre-puberty twins. Our data showed that the BALP activity was influenced both by genetic (54%) and environmental (46%) factors.
authors.affiliation: School of Public Health, Jining Medical University, Jining 272013, China.
authors.forename: Wen-jun
authors.initials: WJ
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Hu
authors.initials: H
authors.lastname: Liu
authors.forename: Qing-sheng
authors.initials: QS
authors.lastname: Kong
authors.forename: Jun-yan
authors.initials: JY
authors.lastname: Zhou
authors.forename: Gui-ying
authors.initials: GY
authors.lastname: Sui
authors.forename: Lei
authors.initials: L
authors.lastname: Deng
mesh_terms: D000293:Adolescent; D000469:Alkaline Phosphatase / Q000097:blood* / Q000235:genetics*; D002118:Calcium / Q000172:deficiency* / Q000378:metabolism; D002136:Calcium, Dietary / Q000378:metabolism; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D011110:Polymorphism, Genetic; D019655:Quantitative Trait, Heritable; D014427:Twins / Q000097:blood* / Q000235:genetics*
chemical_list: D002136:Calcium, Dietary; D000469:Alkaline Phosphatase; D002118:Calcium