Response of parathyroid glands to calcitriol in culture: Is this response mediated by the genetic polymorphisms in vitamin D receptor?

BACKGROUND: Recently, we have developed a model of parathyroid tissue culture that allows the study of the response of the parathyroid glands to long-term effectors, such as calcitriol, and that is also useful to study the likely effect of the genetic polymorphisms in the functionality of the glands. The aim of this study was to evaluate the response to calcitriol of cultured parathyroid tissue from patients with secondary hyperparathyroidism (HPT) and the possible effect of vitamin D receptor (VDR) gene polymorphisms on this response. METHODS: Parathyroid glands (N = 37) from 34 parathyroidectomized patients (17 men, 17 women) were used. Several gland fragments were cultured for 60 hours in the presence of calcitriol 10(-9) mol/L or 10(-8) mol/L. DNA from each fragment was extracted to normalize the hormone secretion levels and to genotype the restriction sites ApaI, BsmI, TaqI, and FokI in the VDR gene. RESULTS: The percentages of secretion observed in the response to calcitriol were: 69%+/- 28% (range, 3-100) and 46%+/- 19% (range, 8-78) for calcitriol 10(-9) mol/L and 10(-8) mol/L, respectively (P = 0.004). None of the polymorphisms showed statistical differences in response to calcitriol with any of the concentrations used. CONCLUSION: Parathyroid glands cultured in vitro from patients with secondary HPT are able to respond to calcitriol decreasing PTH synthesis. These results, however, do not support the current hypothesis that VDR polymorphisms are involved in the modulation of the parathyroid gland response.     

The Contribution of Vitamin D Receptor Gene Polymorphisms in Osteoporosis and Familial Osteoporosis

It is well established that genetic factors play a major role in the pathogenesis of osteoporosis. Previous reports have suggested that vitamin D receptor (VDR) gene polymorphisms, particularly the BB, tt and AA genotypes, are associated with low bone mineral density (BMD). If these VDR genotypes are indeed an important determinant of BMD, then a population of related osteoporotic individuals (mother–daughter or sister–sister relationship) should have a high prevalence of the BB, tt or AA VDR genotypes. To test this hypothesis we determined the VDR genotypes in 26 osteoporotic persons (age 44.3 ± 12.7 years, mean ± SD) belonging to 12 families. Furthermore, for comparison with existing studies, we applied the VDR genotype analysis in a population of 53 unrelated healthy subjects (age 45.2 ± 9.8 years, mean ± SD) and 59 unrelated osteoporotic subjects (age 52.1 ± 9.0 years, mean ± SD). The menopausal status of the healthy and osteoporotic populations was pre-, peri- and mostly early postmenopausal. The proportions of the three genotypes, BB, tt and AA, within the 12 osteoporotic families were 15%, 12% and 27%, respectively, whereas the proportions of the other three homozygous genotypes (bb, TT, aa) were 50%, 50% and 23%. The distribution of the BB, tt and AA genotypes in the normal population was 21%, 21% and 36%, respectively (vs bb, TT, aa: 36%, 38%, 21%), whereas in the osteoporotic population it was 24%, 20% and 34% (vs bb, TT, aa: 27%, 34%, 14%). Our data indicate that there is not a statistically significant (p>0.05) difference in the VDR genotype frequencies within osteoporotic families as compared with the same genotypes in the population of unrelated normal or osteoporotic subjects. VDR genotype analysis showed no significant relation between VDR polymorphisms and BMD or Z-score values at the lumbar spine. This study demonstrates the lack of a heritability pattern between the BB, tt and AA genotypes and low BMD. Received: 29 October 1998 / Accepted: 19 April 1999     

Vitamin D receptor gene polymorphisms modulate the skeletal response to vitamin D supplementation in healthy girls

ObjectivesVitamin D receptor (VDR) gene plays an important role in bone mass regulation. We have previously shown a beneficial effect of vitamin D supplementation on bone mass in girls. This study investigated whether the musculo-skeletal response to Vitamin D was modulated by polymorphisms in VDR gene.DesignRandomized placebo-controlled trial.Methods179 girls (10–17 years), were randomly assigned to placebo or Vitamin D3 for one year. VDR genotypes were determined in 167 girls using BsmI, TaqI and ApaI restriction enzymes. Bone mass at the spine, hip, forearm and total body, and lean mass were measured by DXA at baseline and at one year.ResultsAfter one year, VDR gene polymorphisms using Bsm1 and TaqI restriction enzymes were associated with percent changes in bone area, BMC and BMD at multiple skeletal sites in the Vitamin D3 group but not in the placebo group. The least increments were observed in the BB and tt genotypes. No similar effect was observed with ApaI enzyme. This relationship between VDR genotypes and changes in BMD and BMC remained significant after adjustment for puberty, changes in lean mass, height and bone area.ConclusionVDR gene polymorphisms influence the skeletal response to vitamin D supplementation in healthy adolescent girls.     

Effect of aluminium on osteocalcin production in the rat.

In renal failure, aluminium is an important factor in the development of osteomalacia. The mechanism by which aluminium produces osteomalacia is not clear; it may be toxic to the osteoblast, and as a result of its effect on osteoblasts, impair mineralisation. Another possibility is that aluminium may directly impair mineralisation independent of osteoblast function. Osteocalcin is considered to be a specific marker of osteoblast activity and its production is stimulated by calcitriol. In the present study, calcitriol-stimulated production of osteocalcin was studied as a marker of osteoblast activity in aluminium toxicity. Four groups of rats were evaluated: (1) normals; (2) normal renal function plus aluminium; (3) renal failure; and (4) renal failure plus aluminium. Osteocalcin production was determined by measuring serum osteocalcin at baseline and after stimulation with calcitriol. In rats receiving aluminium, the baseline serum osteocalcin levels were not different from their respective controls. After stimulation with calcitriol, the increase in serum osteocalcin was less in the renal failure group receiving aluminium. However, when corrected for the number of osteoblasts, the increase in serum osteocalcin was not decreased. In summary, although aluminium administration decreased the number of osteoblasts in rats with renal failure, osteocalcin production by the remaining osteoblasts was not decreased.     

Possible influence of vitamin D receptor gene polymorphisms on recombinant human erythropoietin requirements in dialysis patients

BACKGROUND: Vitamin D receptor (VDR) gene polymorphisms have been widely studied, especially to analyze their effects on calcium-phosphorus metabolism and secondary hyperparathyroidism in patients on dialysis. In this study, we sought to investigate the possible effects of these polymorphisms on the anemia of renal failure and recombinant human erythropoietin (rHuEPO) responses among patients receiving hemodialysis. METHODS: One hundred twenty-eight patients (52 females/76 males) underwent genotyping for the insertion/deletion Bsml (B-->b, restriction site, exon VIII-->IX) and Tagl (T-->t, 352 exon IX) VDR gene polymorphisms. The mean value of the last 6 months' monthly evaluated laboratory values (C-reactive protein, hemoglobin, iron indices, PTH, and albumin) and clinical findings (rHuEPO requirement, cumulative iron supplementation doses, and body weight) were analyzed retrospectively excluding patients with chronic inflammation, hemolytic anemia, or active blood loss such as gastrointestinal bleeding. RESULTS: Mean age and dialysis durations were 41.5 +/- 11.8 years and 91.8 +/- 45.3 months, respectively. Polymorphism percentages were as follows: Bsml; BB/Bb/bb: 32.2/63.6/4.2 and Tagl; TT/Tt/tt: 40.5/55.4/4.1%, respectively. BB variant of Bsml gene was related to lower rHuEPO needs (P < .05) and also higher hemoglobin levels (P < .005) when compared with the Bb/bb variant. Considering Tagl variants, transferrin saturation levels were lower (P < .03) among patients with the Tt/tt variant, but there was no other significant difference in the mean values of other data between TT and Tt/tt variants. CONCLUSION: The BB variant of Bsml was related to decreased rHuEPO requirements to achieve higher hemoglobin levels among maintenance hemodialysis patients without chronic inflammation.     

Association of vitamin D receptor gene polymorphism with urolithiasis

PURPOSE: Recent studies suggest that allelic variations of the vitamin D receptor (VDR) gene can influence calcium absorption and excretion. Therefore, we studied the association of VDR gene polymorphism with urolithiasis. SUBJECTS AND METHODS: We studied 83 patients with urinary stones and 83 controls. Patients were scored for certain clinical characteristics, including long axis diameter of the largest stone (1 point-less than 10 mm. and 2-10 mm. or greater), number of stones (1 point-1 and 2-multiple) and history of calcium stone disease (1 point-absent and 2-present). They were classified into 3 groups according to the total score, including low-3, intermediate-4 or 5 and high-6 points. The 2 VDR gene polymorphisms TaqI and ApaI were detected by polymerase chain reaction-restriction fragment length polymorphism and their relationships with the urinary calcium level were examined. RESULTS: The incidence of TaqI Tt and tt genotypes was significantly higher in the high score group than in controls. The TaqI t allele was associated with a 5.2-fold increase in the risk of severe stone disease. The urinary calcium level in patients with the Tt and tt genotypes was also higher than in those with the TT genotype. The rate of the ApaI genotype was not different in the high score group and controls. CONCLUSIONS: The TaqI t allele of the VDR gene may be a risk factor for severe stone disease and recurrent stones.     

Association of the vitamin D receptor genotype BB with low bone density in hyperthyroidism.

Bone mineral density (BMD) is modulated by genetic and environmental factors or certain diseases. In several conditions such as low calcium intake, an influence of vitamin D receptor (VDR) polymorphisms on BMD has been suggested. In the present study, we investigated the relationship of Bsm I and Fok I polymorphisms of the VDR gene and BMD in patients with hyperthyroidism, a disease that often results in low BMD. Bsm I and Fok I genotypes were determined in 76 postmenopausal hyperthyroid patients and 62 healthy postmenopausal women as controls. Patients and controls were matched for age, time since menopause, and lifestyle factors and were free of estrogen medication. BMD evaluation included axial dual X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (PQCT). Low BMD was defined as -2.5 STD below the young adult mean value. Biochemical parameters investigated were thyroid hormones, osteocalcin, and 25-(OH)-vitamin D3 as well as routine laboratory data. Low BMD was found in 61% of hyperthyroid patients and in only 23% of euthyroid controls. In the group of hyperthyroid patients with low bone density, the BB genotype (VDR Bsm I polymorphisms) was significantly more frequent (39%) than in controls (13%; p = 0.003) and hyperthyroid patients with normal BMD (6%; p = 0.013). The odds ratio (OR) for low BMD in patients with BB genotype was 5.7 (95% CI, 1.7-19.1; p < 0.005) as compared with the Bb and bb genotypes and 5.5 (95% CI, 2.3-13.2; p < 0.0001) for hyperthyroidism alone. The cumulative risk for low BMD in patients with hyperthyroidism and BB genotype was 31.4 (95% CI, 3.9-256; p < 0.0003). VDR Fok I genotypes showed no significant relationship with BMD or other general or bone-specific parameters. Thus, hyperthyroidism and the genetic background of a BB genotype may promote synergistically the development of low BMD in hyperthyroid patients. Screening for the BB genotype in these patients therefore could help to identify those with particularly high risk for the development of low BMD and allow early treatment.     

Vitamin D Receptor Genotypes and Intestinal Calcium Absorption in Postmenopausal Women

Several studies have shown that bone mass and bone turnover are genetically determined. This genetic component is thought to be mediated in part by polymorphisms at the vitamin D receptor (VDR) locus, even though the underlying molecular mechanisms are still unknown. To evaluate a possible site of differential action of the VDR gene alleles we examined their correlation with intestinal calcium absorption in 120 Caucasian postmenopausal women (aged 61 ± 0.6 years). VDR gene polymorphisms for Apa I, Bsm I, and Taq I restriction endonucleases were assessed by Southern blotting analysis. The most common genotypes observed in our population were AaBbTt (37%), AABBtt (20%), aabbTT (15%), AabbTT (15%), and AABbTt (9%). Although there was some evidence of 13% higher lumbar BMD values in aabbTT genotype with respect to AABBtt genotype, this difference of approximately 0.1 g/cm² did not reach statistical significance, possibly because of the limited number of observations. On the contrary, no relationship was found between genotypes and femoral neck BMD values. Intestinal calcium absorption was significantly lower in BB and tt genotypes than, in bb and TT genotypes, respectively, and in AABBtt genotype than in either aabbTT or AaBbTt genotypes (P= 0.0015 ANOVA). No significant differences in intact PTH, alkaline phosphatase, 25OHD₃, and 1,25(OH)₂D₃ were found among subjects with different VDR genotypes. These results are consistent with a possible role of VDR alleles on intestinal calcium absorption.     

老年男性维生素D受体基因多态性与骨密度关系的研究

目的研究维生素D受体(vitamin D receptor,VDR)基因多态性在老年男性中的分布, 并进一步研究其与骨密度的关系。方法采用聚合酶链反应-限制性片段长度多态性(PCR- RFLP)方法,分析145例老年男性的VDR基因型,同时用双能X线吸收法测定腰椎及髋部骨密度。结果 VDR基因型分别为BB,0．014;Bb,0．117;bb,0．869。骨质疏松组与非骨质疏松组之间VDR基因型分布频率的差异无显著性(P>0．05)。比较各基因型组的骨密度,bb组及 Bb组只有在股骨颈处显示出BMD均低于BB组,差异有显著性(P<0．05),其它部位,三个基因型组的BMD均差异无显著性(P>0．05)。结论老年男性VDR基因型分布频率与某些西方国家人群分布不同,其VDR基因型与骨密度无明显相关性。VDR基因可能不是我们所研究群体 BMD的主要遗传基因。     

Influence of Bsml vitamin D receptor gene polymorphism on the response to a single bolus of calcitrol in hemodialysis patients

AIMS: BsmI polymorphism of the vitamin D receptor gene has been linked to hyperparathyroidism severity and calcitriol levels. The aim of this study was to analyze the response to a single bolus of calcitriol in hemodialysis patients with the BB and bb genotype. PATIENTS: Twenty homozygous BsmI hemodialysis patients (9 BB and 11 bb). METHODS: Hyperparathyroidism was assessed comparing basal PTH levels, and in 17 patients, also measuring the inhibition with hypercalcemia. Patients were given a bolus of calcitriol and PTH in absolute terms and in percentages relative to the baseline values at 24, 48 and 72 hours after the bolus were measured. All biochemical parameters were compared between genotypes with univariant ANOVA and additionally, PTH relative values were compared with general factorial analysis of variance, adjusting for calcium and phosphorus. Means were also compared within each genotype between consecutive determinations with non-parametric Wilcoxon analysis, using each patient as his/her own control. The response to calcitriol was also assessed by the area under the curve for each patient and was subsequently compared between genotypes. RESULTS: There were no differences on hyperparathyroidism severity between the groups. The BB genotype showed a better response than bb to calcitriol 72 hours after the bolus (percentage relative to basal PTH value: BB: 63%, bb: 88.6%, p = 0.03; BB vs bb with univariant ANOVA). When general factorial analysis of variance was applied, adjusting for serum calcium and phosphorus, genotype showed a significant influence on the response to calcitriol at 72 hours (p = 0.04). When each patient was used as his/her own control, the BB genotype showed a significant decrease in PTH levels at 48 and 72 hours (p = 0.00 baseline vs 48 h, and p = 0.01 baseline vs 72h) whereas the bb did not. CONCLUSIONS: BsmI polymorphism of the VDR gene induces differences on the response to a single bolus of calcitriol independently of calcium and phosphorus.     

维生素D受体基因型与骨密度

目的考察维生素D受体(VDR)基因多态性在我国汉族人群中的分布频率,分析VDR基因型与骨密度的关系.方法采用聚合酶链反应和限制性酶切技术检测100例绝经前健康妇女VDR基因多态性.应用双能X线骨密度仪检测受试者腰椎及髋部骨密度.结果VDR基因型分布频率为BB型4.0%,Bb型10.0%,bb型86.0%;而三种基因型受试者髋部及腰椎骨密度均表现出Bb＞bb＞BB,经F检验腰椎骨密度3基因型比较,P＜0.05,具有显著差异.结论绝经前妇女VDR基因型分布频率与西方及国内的一些报道不尽相同,且骨密度显示出Bb＞bb＞BB,亦与国内外一些研究结果不同.     

Lack of association between vitamin D receptor gene polymorphism (BsmI) and osteomalacia

Vitamin D receptor (VDR) gene polymorphism has been reported to be a determinant of bone formation and intestinal calcium absorption. We carried out this study to assess the role of VDR gene polymorphism in the pathogenesis of osteomalacia. We investigated BsmI polymorphisms in the gene encoding the 1,25 dihydroxyvitamin D receptor in 38 patients with osteomalacia and 31 healthy controls, along with examination of serum calcium, phosphorus, alkaline phosphatase, parathyroid hormone, and 25 hydroxyvitamin D levels. VDR allelic variants were: BB, 31.6%; Bb, 44.7%; and bb, 23.7% in the osteomalacia patients and BB, 19.4%; Bb, 61.3%; and bb, 19.4% in the controls. Although heterozygotes (Bb) were more frequent than other genotypes in both groups, the BB genotype was found to be more prevalent in osteomalacia than in controls. There was no statistical relationship between VDR genotype and osteomalacia. It is concluded that, in this small group of patients, there was no relationship between VDR allelic polymorphisms and osteomalacia.     

Does the vitamin D receptor genotype predict bone mineral loss in haemodialysed patients?

Background. It has been suggested that the vitamin D receptor (VDR) gene BsmI-polymorphism is a genetic determinant of bone metabolism. Design. To test this hypothesis, the relationship between VDR genotypes, bone mineral density (baseline and after 18 months) and parameters of calcium metabolism and bone turnover were investigated prospectively in 88 haemodialysed patients not receiving active vitamin D metabolites. Methods. Whole body, lumbar spine and femoral neck bone mineral density (BMD) were assessed by dual energy X-ray absorptiometry (DEXA). In addition calcium, phosphorus, 25(OH)D3, 1,25(OH)2D3, osteocalcin serum concentrations, alkaline phosphatase activity and intact, 1,84 PTH levels were measured. Results. VDR genotype BB, Bb and bb were found in 27, 49 and 24% of patients. Initial BMD (g/cm²) of whole body, lumbar spine and femoral neck did not differ between genotypes (whole body: BB 1.055 ± 0.120, Bb 1.082 ± 0.102, bb 1.128 ± 0.120; lumbar spine: BB 1.075 ± 0.199, Bb 1.079 ± 0.185, bb 1.099 ± 0.170; femoral neck: BB 0.808 ± 0.160, Bb 0.862 ± 0.127, bb 0.842 ± 0.125; mean ± SD), but the decrease of whole body and femoral neck BMD during 18 months was significantly (P < 0.02) different between the genotype groups (whole body: BB -0.048 ± 0.028, Bb -0.031 ± 0.029, bb -0.024 ± 0.023; femoral neck BB -0.044 ± 0.069, Bb -0.032 ± 0.081, bb -0.012 ± 0.029 g/cm²). Conclusions. This preliminary study suggests faster mineral loss in BB genotype of VDR in haemodialysed patients.     

Association between two types of vitamin d receptor gene polymorphism and bone status in premenopausal Japanese women

Polymorphisms in the vitamin D receptor (VDR) gene using ultrasound (US) bone mass and bone metabolic markers were investigated as potential genetic markers for osteoporosis in 126 premenopausal Japanese women aged 27.2 +/- 10.1 (mean +/- SD) years. The relationship between their VDR gene polymorphisms and bone states was determined. VDR genotypes were based on the absence (B) or presence (b) of the Bsm I restriction site (B polymorphism), and ATG (the M allele) and ACG (the m allele) sequences at the translation initiation site (M polymorphism). Genotype frequencies were 73.8%, bb; 24.6%, Bb; 1.6%, BB; 15.1%, MM; 51.6%, Mm and 33.3%, mm. The stiffness index of calcaneal bone minerals measured by an US bone densitometer was significantly higher in the mm types (P <0.05 versus MM) than in the Mm types (P <0.01 versus MM) and MM types. There was no significant difference between in B polymorphisms. Furthermore, bone mass was correlated with serum bone type alkaline phosphatase (ALP) activity and urinary deoxypyridinoline concentration in M polymorphisms. Because the distribution of B polymorphisms in each M polymorphism genotype did not differ, M polymorphisms were affected independently from B polymorphisms to bone mass or bone metabolic markers. No significant difference was observed in nutritional intake and food consumption among genotypes. In the MM and Mm types, the bone mass was closely related to the frequency of milk intake during the periods of elementary and junior high school. In contrast, bone mass was not associated with nutritional intake or the frequency of past milk intake in B polymorphisms. Therefore, the M polymorphism of the VDR gene is a stronger genetic indicator of osteoporosis than the B polymorphism in premenopausal Japanese woman.     

Polymorphisms in the vitamin D receptor gene and the risk of calcium nephrolithiasis in children

OBJECTIVE: Polymorphism in the Vitamin D Receptor (VDR) gene has recently been reported to be associated with calcium metabolism disorders. This study was conducted to investigate the association of VDR gene polymorphism with the risk of calcium nephrolithiasis. METHODS: We investigated the VDR ApaI, BsmI and TaqI polymorphisms, in relation to serum calcium, phosphate, intact parathyroid hormone and 1.25(OH)(2)D(3) in 64 hypercalciuric stone-forming children and 90 healthy children. DNA was isolated from peripheral blood, and genotyping was performed with PCR-based methods. RESULTS: The frequency of ApaI AA genotype was significantly higher in the children with calcium nephrolithiasis than the controls (chi(2)=9.5; p=0.008). The distribution of BsmI and TaqI genotypes in stone-forming patients was similar to those in the control group. There was a significant association between TaqI TT genotype and the strength of the family history. The patients with TT genotype were observed to have a 8 times more risk than patients with Tt/tt genotype for recurrent stone episodes (OR 8, 95%CI 1.61-39.6). CONCLUSION: VDR genotype determination may provide a tool to identify individuals who are at a risk for calcium nephrolithiasis.     

VDR Genotype and Response to Etidronate Therapy in Late Postmenopausal Women

Twenty-four late postmenopausal women with osteoporosis were studied. The patients were separated in three subgroups according to the BsmI polymorphism of the vitamin D receptor (VDR) gene: BB (n= 8), Bb (n = 10) and bb (n = 6). They did not differ in age (mean ages were 66.0 years, 65.9 years and 63.9 years, respectively), years after menopause (18.7 years, 18.1 years and 18.4 years) or body weight (64.9 kg, 65.3 kg and 63.8 kg), the variables known to be associated with bone mineral density (BMD). The results show that the response to antiresorptive bisphosphonate therapy in combination with calcium supplementation is modified by VDR genotype. The lumbar spine BMD increased significantly faster in the BB and Bb groups (7.3% and 7.0%, respectively) compared with the bb group (2.5%) during 1 year of cyclic etidronate therapy (400 mg/day) and calcium supplementation (1000 mg/day). The biochemical marker of bone resorption (urinary hydroxyproline excretion) as well as the bone formation marker (serum levels of osteocalcin) decreased during the treatment. With respect to VDR genotype, a significantly higher decrease in osteocalcin level was observed in bb as compared with BB subjects. We conclude that the VDR genotype is involved in an individual’s response to cyclic etidronate therapy with calcium supplementation. Received: 12 December 1998 / Accepted: 18 March 1999     

Vitamin D receptor gene polymorphisms and prostate cancer risk

BACKGROUND: Vitamin D is a steroid hormone that is thought to play a role in the etiology and progression of prostate cancer. Hormone activity requires binding to the vitamin D receptor (VDR), which contains several genetic polymorphisms that have been associated with risk of prostate cancer. To further evaluate this relationship, we conducted a population-based case-control study of the VDR BsmI, FokI, and Poly-A polymorphisms, and prostate cancer. METHODS: Germline DNA samples and survey data from incident prostate cancer cases (n = 559) and controls (n = 523) of similar age (40-64 years) without a history of the disease who resided in King County, Washington were analyzed. RESULTS: The frequency of the BsmI, FokI, and Poly-A genotypes were similar in cases and controls, and no overall association between any variants and prostate cancer risk were noted. Stratification by clinical features of disease revealed that among men with localized stage disease, the BsmI bb genotype was associated with a modest increase in risk (OR, 1.49; 95% CI, 1.02-2.17; P = 0.04) compared to the BB genotype. CONCLUSIONS: These results suggest that polymorphisms in the VDR gene are not strong predictors of prostate cancer risk among Caucasian men in the U.S.     

Gene polymorphisms,bone mineral density and bone mineral content in young children:the Iowa bone development study

We examined the association of candidate gene polymorphisms with bone mineral density (BMD) and bone mineral content (BMC) in a cohort of 428 healthy non-Hispanic white children participating in the Iowa Bone Development Study, a longitudinal study of determinants of bone accrual in childhood. BMD and BMC measurements of the hip, spine and whole body were made using a Hologic 2000 Plus densitometer in 228 girls and 200 boys ages 4.5–6.5 years. Genotypes at 14 loci representing eight candidate genes [type I collagen genes (COL1A1 and COL1A2), osteocalcin, osteonectin, osteopontin, vitamin D receptor (VDR), estrogen receptor (ER), androgen receptor (AR)] were determined. Gender-specific and gender-combined prediction models for bone measures that included age, weight, height (and gender) were developed using multiple linear regression analysis. COL1A2 and osteocalcin genotypes were identified as having the strongest and most consistent association with BMD/BMC measures. Osteonectin, osteopontin and VDR translation initiation site polymorphisms were associated with some individual bone measures, but none of the associations was as consistent as those identified for the COL1A2 and osteocalcin genes. No association was identified with COL1A1 (RsaI and Sp1), VDR (BsmI) and ER polymorphisms (PvuII, XbaI, TA) and BMD/BMC. However, we identified significant gene-by-gene interaction effects involving the ER and both VDR and osteocalcin, which were associated with BMD/BMC. Our data suggest that genetic variation at multiple genetic loci is important in bone accrual in children. Moreover, the combination of genotypes as several loci may be as important as a single genotype for determining BMD and BMC.