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1,25-dihydroxyvitamin D and the vitamin D receptor gene polymorphism Apa1 influence bone mineral density in primary hyperparathyroidism.

ABSTRACT: OBJECTIVE: Parathyroid hormone (PTH) and vitamin D are the most important hormones regulating calcium metabolism. In primary hyperparathyroidism (PHPT) excessive amounts of PTH are produced. Bone turnover is enhanced, leading to reduced bone mineral density and elevated levels of serum calcium. The aim of this study was to investigate relations between serum levels of 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)(2)D) and bone mineral density, as well as known genetic polymorphisms in the vitamin D receptor and enzymes metabolising vitamin D in patients with PHPT. DESIGN/SUBJECTS: We conducted a cross-sectional study of 52 patients with PHPT. RESULTS: Mean level of 25(OH)D was 58.2 nmol/L and median 1,25(OH)(2)D level was 157 pmol/L. Among our patients with PHPT 36.5% had 25(OH)D levels below 50 nmol/L. Serum 1,25(OH)(2)D was inversely correlated to bone mineral density in distal radius (p?=?0.002), but not to bone mineral density at lumbar spine or femoral neck. The vitamin D receptor polymorphism Apa1 (rs7975232) was associated with bone mineral density in the lumbar spine. CONCLUSIONS: The results suggest that PHPT patients with high blood concentrations of 1,25(OH)(2)D may have the most deleterious skeletal effects. Randomized, prospective studies are necessary to elucidate whether vitamin D supplementation additionally increases serum 1,25(OH)(2)D and possibly enhances the adverse effects on the skeleton in patients with PHPT.

SUBMITTER: Christensen MH

PROVIDER: S-EPMC3572149 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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1,25-dihydroxyvitamin D and the vitamin D receptor gene polymorphism Apa1 influence bone mineral density in primary hyperparathyroidism.

Christensen Monika H E MH Apalset Ellen M EM Nordbø Yngve Y Varhaug Jan Erik JE Mellgren Gunnar G Lien Ernst A EA

PloS one 20130213 2

<h4>Objective</h4>Parathyroid hormone (PTH) and vitamin D are the most important hormones regulating calcium metabolism. In primary hyperparathyroidism (PHPT) excessive amounts of PTH are produced. Bone turnover is enhanced, leading to reduced bone mineral density and elevated levels of serum calcium. The aim of this study was to investigate relations between serum levels of 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)(2)D) and bone mineral density, as well as known genetic p ...[more]

PMID: 23418495

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Project description:A subset of PHPT patients exhibit a more severe disease phenotype characterized by bone loss, fractures, recurrent nephrolithiasis, and other dysfunctions, but the underlying reasons for this disparity in clinical presentation remain unknown.We sought to identify new mechanistic indices that could inform more personalized management of PHPT.Pre-, peri-, and postoperative data and demographic, clinical, and pathological information from patients undergoing parathyroidectomy for PHPT were collected. Univariate and partial Spearman correlation was used to estimate the association of parathyroid tumor calcium sensing capacity with select variables.An unselected series of 237 patients aged >18years and undergoing parathyroidectomy for PHPT were enrolled.Calcium sensing capacity, expressed as the concentration required for half-maximal biochemical response (EC50), was evaluated in parathyroid tumors from an unselected series of 74 patients and assessed for association with clinical parameters. The hypothesis was that greater disease severity would be associated with attenuated calcium sensitivity and biochemically autonomous parathyroid tumor behavior.Parathyroid tumors segregated into two distinct groups of calcium responsiveness (EC50<3.0 and ?3.0mM). The low EC50 group (n=27) demonstrated a mean calcium EC50 value of 2.49mM [95% confidence interval (CI): 2.43-2.54mM], consistent with reference normal activity. In contrast, the high EC50 group (n=47) displayed attenuated calcium sensitivity with a mean EC50 value of 3.48mM [95% CI: 3.41-3.55mM]. Retrospective analysis of the clinical registry data suggested that high calcium EC50 patients presented with a more significant preoperative bone mineral density (BMD) deficit with a t-score of -2.7, (95% CI: -3.4 to -1.9) versus 0.9, (95% CI: -2.1 to -0.4) in low EC50 patients (p<0.001). After adjusting for gender, age, BMI, 25 OH vitamin D level and preoperative iPTH, lowest t-score and calcium EC50 were inversely correlated, with a partial Spearman correlation coefficient of -0.35 (p=0.02).Impaired calcium sensing in parathyroid tumors is selectively observed in a subset of patients with more severe bone mineral density deficit. Assessment of parathyroid tumor biochemical behavior may be a useful predictor of disease severity as measured by bone mineral density in patients with PHPT.

Project description:BACKGROUND: Primary hyperparathyroidism (PHPT) affects mainly cortical bone. It is thought that parathyroid hormone (PTH) indirectly regulates the activity of osteoclasts by means of the osteoprotegerin/ligand of the receptor activator of nuclear factor-κβ (OPG/RANKL) system. Several studies have confirmed that OPG (osteoprotegerin) and RANKL (ligand of the receptor activator of nuclear factor-κβ) loci are determinants of bone mineral density (BMD) in the general population. The aim of this study is to analyze the relationship between fractures and BMD and the rs3102735 (163 A/G), rs3134070 (245 T/G) and rs2073618 (1181 G/C) SNPs of the OPG and the rs2277438 SNP of the RANKL, in patients with sporadic PHPT. METHODS: We enrolled 298 Caucasian patients with PHPT and 328 healthy volunteers in a cross-sectional study. We analyzed anthropometric data, history of fractures or renal lithiasis, biochemical determinants including markers for bone remodelling, BMD measurements in the lumbar spine, total hip, femoral neck and distal radius, and genotyping for the SNPs to be studied. RESULTS: Regarding the age of diagnosis, BMI, menopause status, frequency of fractures or renal lithiasis, we found no differences between genotypes in any of the SNPs studied in the PHPT group. Significant lower BMD in the distal radius with similar PTH levels was found in the minor allele homozygotes (GG) compared to heterozygotes and major allele homozygotes in both OPG rs3102735 (163 A/G) and OPG rs3134070 (245 T/G) SNPs in those with PHPT compared to control subjects. We found no differences between genotypes of the OPG rs2073618 (1181 G/C) SNP with regard to BMD in the PHPT subjects. In the evaluation of rs2277438 SNP of the RANKL in PHPT patients, we found a non significant trend towards lower BMD in the 1/3 distal radius and at total hip in the minor allele homocygotes (GG) genotype group versus heterocygotes and major allele homocygotes (AA). CONCLUSIONS: Our study provides the first evaluation of the relationship between SNPs of the OPG/RANK system and sporadic PHPT. Subjects with PHPT and minor homocygote genotype (GG) for the OPG rs3102735 (163 A/G) and OPG rs3134070 (245 T/G) SNPs have lower BMD in the distal radius, and this association does not appear to be mediated by differences in PTH serum levels.

Dataset Information

1,25-dihydroxyvitamin D and the vitamin D receptor gene polymorphism Apa1 influence bone mineral density in primary hyperparathyroidism.

Publications

1,25-dihydroxyvitamin D and the vitamin D receptor gene polymorphism Apa1 influence bone mineral density in primary hyperparathyroidism.

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