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Objective: To explore the relationships among serum25OHD, iPTH and bonemetabolism markers in health children; to intact the changes of serum25OHD,iPTH and bone metabolism markers along with age.Methods: The subjects were150health children,85boys and65girls, whocame to Division of Nutrition, Growth and Development&Endocrinology ofDepartment of Pediatrics, Second Hospital of Hebei Medical Universityduring December2012and March2013. All the children were health and theirlegal guardians provided written informed consent in accordance with theEthics Committees of the Second Hospital of Hebei Medical University. Allthe subjects were divided into4subgroups according to their age:0-1yr,1-3yr,3-7yr and7-14yr representing infancy, preschool, school age and adolescencerespectively. According to serum25OHD levels, children were divided into4groups like <27.5nmol/L,27.5-50nmol/L,50-75nmol/L and>75nmol/Lgroups. All the subjects were grouped based on serum iPTH levels as<1pmol/L,1-1.5pmol/L,1.5-2pmol/L and>2pmol/L. Serum25OHD, BAP,OC and urine-DPD were assayed by ELSIA. Serum iPTH was assayed byCLIA and serum ALP, Ca, P and urine-Cr were assayed by auto-biochemistryanalytical instrument. Data were analyzed by using SPSS19.0for Windowssoftware (SPSS Inc. Chicago). All data were not normally distributed analyzedby Normality Tests, so they were showed as Mean±SD or median (25%,75%).Medians among groups were computed and compared by using K-W Tests.The relevancies between variables were analyzed by adjusted partialcorrelation test. Differences were considered as significant at P<0.05.Results:1. The average serum25OHD level of all the subjects was51.30(37.78,69.97)nmol/L, iPTH1.40(1.10,1.95)pmol/L,BAP61.57±21.95U/L,OC54.09±30.57ng/ml, u-DPD/Cr28.74(20.86,37.34), ALP225.38±59.29U/L， Ca2.62±0.27mmol/L，P1.77±0.24mmol/L； the average serum25OHD levelof85boys was50.20(38.98,69.15)nmol/L, iPTH1.30(1.00,1.75)pmol/L,BAP61.21±17.71U/L, OC51.43±25.55ng/ml, u-DPD/Cr28.32(20.38,38.54),ALP231.46±52.71U/L, Ca2.64±0.15mmol/L, P1.77±0.17mmol/L; the averageserum25OHD level of65girls was25OHD51.30(37.45,75.91)nmol/L,iPTH1.60(1.00,2.10)pmol/L, BAP64.35±26.54U/L, OC57.58±36.02ng/ml,u-DPD/Cr29.69(21.78,36.55), ALP217.30±66.61U/L, Ca2.60±0.37mmol/L,P1.75±0.31mmol/L; there was no difference between genders of all theresults(P>0.05).2. Changes of serum25OHD, iPTH and bone metabolismmarkers along with age: all the subjects were divided into4subgroupsaccording to their age:0-1yr,1-3yr,3-7yr and7-14yr representing infancy,preschool, school age and adolescence respectively. The average levels ofserum BAP in the4groups were67.45±31.18U/L,58.94±15.98U/L,62.07±12.48U/L and61.70±21.40U/L respectively; the average levels ofserum OC in the4groups were36.31±15.82ng/ml,45.46±16.09ng/ml,64.75±39.35ng/ml and72.30±32.80ng/ml; the median levels of serum25OHDin the4groups were79.57nmol/L,49.10nmol/L,45.75nmol/L and43.35nmol/L; the median levels of serum iPTH in the4groups were1.40pmol/L,1.20pmol/L,1.70pmol/L and1.50pmol/L; the median levels ofthe urine DPD/Cr were29.78,25.96,15.12,18.76. So along with the increaseof age, serum25OHD decreased and there was difference between group1and others3groups (P<0.001). Along with the increase of age, urine-DPDdecreased and there were differences between group1and group3,4(P<0.05);serum OC levels increased and there were differences between group1andgroup3,4(P<0.05); there were no obvious changes of other markers.3. Relationship between Serum25-hydroxyvitamin D, Parathyroid hormoneand Bone Metabolism Markers in children:3.1According to serum25OHDlevels, children were divided into4groups like <27.5nmol/L,27.5-50nmol/L,50-75nmol/L and>75nmol/L groups. The average levels of serum BAP were52.95±15.42U/L,64.16±18.53U/L,61.71±19.20U/L and70.84±34.29U/L; theaverage levels of serum OC were60.64±20.51ng/ml,68.55±38.63ng/ml, 48.33±24.10ng/ml and39.12±20.25ng/ml; the median levels of urine DPD/Crwere22.17,24.70,28.65and34.94. So along with the increase of serum25OHD, serum OC levels decreased and there were differences between group4and group1,2(P<0.05) and group2and3(P<0.05). All the subjects weregrouped based on serum iPTH levels as <1pmol/L,1-1.5pmol/L,1.5-2pmol/Land>2pmol/L. The average levels of serum BAP were51.64±18.26U/L,64.74±28.68U/L,63.84±19.69U/L and69.78±16.95U/L; the average levels ofserum OC were50.14±24.19ng/ml,9.39±24.52ng/ml,51.35±22.74ng/ml and70.79±48.80ng/ml; the median levels of urine DPD/Cr were22.64,30.14,23.57and29.31. So along with the increase of iPTH, BAP increasedobviously and there were differences between group1and group3,4(P<0.05).Serum OC levels increased and there were differences between group4andgroup2,3(P<0.05).3.2The relevancies between25OHD, iPTH and bonemetabolism markers were analyzed by adjusted partial correlation test. SerumOC was negatively related to25OHD (R=-0.182, P=0.03) and positivelyrelated to iPTH(R=0.30, P<0.001). There were no differences among othermarkers.3.3The correlation between serum ALP and BAP:3.3.1Therelevancy between ALP and BAP was analyzed by adjusted partial correlationtest of different ages. We found that there was obvious positive relationbetween serum ALP and BAP of children in different age groups(R=0.719,P<0.001).3.3.2The relevancy between ALP and BAP was analyzed byadjusted partial correlation test of different gender. We found that there wasobvious positive relation between serum ALP and BAP of children in differentgender.Conclusion:1.The serum25OHD, iPTH and bone metabolism markers ofchildren changes along with age.2. Serum25OHD and iPTH closely relatedto bone metabolism markers; however it is not clear whether to conclude thesuitable25OHD level through the bone metabolism markers.3. ALP and BAPare positively related and we may use ALP instead of BAP to intact the bonemetabolism of children.
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