Baseline bone turnover marker levels can predict change in bone mineral density during antiresorptive treatment in osteoporotic patients: the Copenhagen bone turnover marker study

Anti-resorptive osteoporosis treatment might be more effective in patients with high bone turnover. In this registry study including clinical data, high pre-treatment bone turnover measured with biochemical markers was correlated with higher bone mineral density increases. Bone turnover markers may be useful tools to identify patients benefitting most from anti-resorptive treatment.

INTRODUCTION

In randomized, controlled trials of bisphosphonates, high pre-treatment levels of bone turnover markers (BTM) were associated with a larger increase in bone mineral density (BMD). The purpose of this study was to examine this correlation in a real-world setting.

METHODS

In this registry-based cohort study of osteoporosis patients (n = 158) receiving antiresorptive therapy, the association between pre-treatment levels of plasma C-telopeptide of type I Collagen (CTX) and/or N-terminal propeptide of type I procollagen (PINP) and change in bone mineral density (BMD) at lumbar spine, total hip, and femoral neck upon treatment was examined. Patients were grouped according to their pre-treatment BTM levels, defined as values above and below the geometric mean for premenopausal women.

RESULTS

Pre-treatment CTX correlated with annual increase in total hip BMD, where patients with CTX above the geometric mean experienced a larger annual increase in BMD (p = 0.008) than patients with CTX below the geometric mean. The numerical pre-treatment level of CTX showed a similar correlation at all three skeletal sites (total hip (p = 0.03), femoral neck (p = 0.04), and lumbar spine (p = 0.0003)). A similar association was found for PINP where pre-treatment levels of PINP above the geometric mean correlated with a larger annual increase in BMD for total hip (p = 0.02) and lumbar spine (p = 0.006).

CONCLUSION

Measurement of pre-treatment BTM levels predicts osteoporosis patients' response to antiresorptive treatment. Patients with high pre-treatment levels of CTX and/or PINP benefit more from antiresorptive treatment with larger increases in BMD than patients with lower pre-treatment levels.

Osteogenesis imperfecta and the teeth, eyes, and ears-a study of non-skeletal phenotypes in adults

Osteogenesis imperfecta (OI) is a disease causing bone fragility; however, it potentially affects all organs with a high content of collagen, including ears, teeth, and eyes. The study is cross-sectional and compares non-skeletal characteristics in adults with OI that clinicians should be aware of when caring for patients with OI.

INTRODUCTION

Osteogenesis imperfecta (OI) is a hereditary connective tissue disorder. The skeletal fragility is pronounced; however, OI leads to a number of extra-skeletal symptoms related to the ubiquity of collagen type 1 throughout the human body. The vast majority of knowledge is derived from studies performed in the pediatric population. Thus, we aimed to investigate the nature and prevalence of ophthalmologic, odontologic, and otologic phenotypes in an adult population with OI.

METHODS

The study population comprises 85 Danish OI patients (age 44.9 ± 15.9 years). Fifty-eight patients had OI type I, 12 OI type III, and 15 OI type IV according to the classification by Sillence. Audiometric evaluations and dental examinations were performed in 62 and 73 patients, respectively. Ophthalmologic investigations were performed in 64 patients, including measurements of the central corneal thickness.

RESULTS

All patients, except two, had corneal thickness below the normal reference value. Patients with OI type I and patients with a quantitative collagen defect had thinner corneas compared to patients with OI type III and other patients with a qualitative collagen defect. One patient in this cohort was diagnosed with and treated for acute glaucoma. Dentinogenesis imperfecta was diagnosed in one fourth of the patients, based on clinical and radiographic findings. This condition was predominately seen in patients with moderate to severe OI. Hearing loss requiring treatment was found in 15 of 62 patients, of whom three were untreated. The most prevalent type of hearing loss (HL) was sensorineural hearing loss, whereas conductive HL was solely seen in patients with OI type III. The patients with the most severe degrees of HL were patients with mild forms of OI. Age was associated with increased HL.

CONCLUSION

Although significant health problems outside the skeleton are frequent in adult patients with OI, the patients are not consistently monitored and treated for their symptoms. Clinicians treating adult patients with OI should be aware of non-skeletal health issues and consider including regular interdisciplinary check-ups in the management plan for adult OI patients.

Hyponatremia, a risk factor for osteoporosis and fractures in women

SUMMARY

Hyponatremia has been linked to an increased risk of osteoporosis and fractures. We found an increased hazard ratio of major osteoporotic fractures adjusted for potential confounders, including osteoporosis and medication. A reduced BMD was not sufficiently explaining the association. Our data indicate that hyponatremia should be considered a risk factor for osteoporosis and fractures.

INTRODUCTION

Hyponatremia is the most common electrolyte disorder in clinical practice and could be a risk factor for both osteoporosis and fractures. Mild hyponatremia has traditionally been regarded as a benign and asymptomatic condition; however, data from large population and animal studies have led to a reappraisal of this view. The purpose of this study was to evaluate the association of hyponatremia with osteoporosis and major osteoporotic fractures (MOF) in women.

METHODS

This is a historical cohort study with fracture follow-up. The study consisted of 5610 patients with available serum sodium and a bone density measurement. Information on potential risk factor was obtained through a questionnaire. Additional information on medication, comorbidities, and fractures was obtained through national registries.

RESULTS

Hyponatremia was associated with significant lower T-scores at total hip and a borderline significant lower T-score at femoral neck in the multivariate analysis. No association was found between hyponatremia and the lumbar spine T-score. Hyponatremia was associated with an increased hazard ratio of sustaining a MOF in the period from 6 months prior to 12 months after serum sodium measurement. Finally, data showed a relationship with increasing serum sodium and an increasing T-score estimate and a decreasing hazard ratio of MOF.

CONCLUSIONS

Our data suggest that hyponatremia in women increases the risk of osteoporosis and MOF. The increased risk of MOF was independent of osteoporosis.

Subsequent fracture rates in a nationwide population-based cohort study with a 10-year perspective

SUMMARY

Fractures after the age of 50 are frequently observed in Denmark, and many of these may be osteoporotic. This study examined the incidence of all and subsequent fractures in a 10-year period from 2001 to 2011. The incidence of subsequent fractures was high, especially following hip fracture.

INTRODUCTION

The purpose of this study is to examine patterns of subsequent fractures and mortality rates over a 10-year period in patients already suffering from fracture.

METHODS

The study was designed as a nationwide, register-based follow-up study. Patients were included if diagnosed with an index fracture (ICD-10 codes: S22.x, S32.x, S42.x, S52.x, S62.x, S72.x, S82.x, S92.x, T02.x, T08.x, T10.x and T12.x) between January 1st, 2001 and December 31st, 2001 and if older than 50 years at time of fracture. The patients were investigated for future subsequent fractures from January 1st, 2002 to December 31st, 2011.

RESULTS

In this study, we demonstrated that patients with fractures (especially hip fractures) have a high risk of subsequent fractures, especially hip fracture. Other fractures, which are not commonly considered as osteoporotic fractures, such as lower leg, were frequently observed in the 10 years following index fracture. The cumulative incidence proportion (CIP) of subsequent fractures during the 10-year follow-up period was high for all recurrent fractures (9-46 %). Subsequent hip fracture, regardless of index fracture, had the highest CIP across the study period, ranging from 9 to 40 %. Appendicular fractures were often followed by a recurrent fracture, or subsequent fractures at a more proximal location in the same limb, i.e. forearm fractures were followed by humerus fractures. These results have not been previously demonstrated to this extent, and according to our knowledge, no previous studies have estimated cumulative 10-year subsequent fracture incidences for any non-hip fractures.

CONCLUSION

Patients suffering a fracture (and especially a hip fracture) have a high incidence of subsequent fracture. Fractures after the age of 50 may be considered an early warning of increased risk for future fractures in many patients.

Newborn regional body composition is influenced by maternal obesity, gestational weight gain and the birthweight standard score

AIM

This study investigated whether newborn body composition is influenced by prepregnancy obesity and gestational weight gain (GWG) and explored any associations between body composition and birthweight standard score (z-score), categorised by size for gestational age.

METHODS

We recruited 231 obese and 80 normal weight mothers and their newborn infants and assessed the babies' body composition using dual-energy X-ray absorptiometry.

RESULTS

The total and abdominal fat masses of infants born to mother who were obese before pregnancy were 135 g (p < 0.001) and 18 g (p < 0.001) higher than the offspring of normal weight mothers. The infants' fat mass increased by 11 g (p < 0.001) for every kilogram of GWG. There were no associations between prepregnancy obesity and fat-free mass. The fat percentage was significantly higher in infants who were large for gestational age (15.3%) than small for gestational age (5.2%) and appropriate for gestational age (9.8%) (p < 0.001). Lower birthweight z-score was associated with a higher proportion of abdominal fat mass (p = 0.009).

CONCLUSION

Infants born to obese mothers had higher fat mass at birth, with abdominal fat accumulation. Low birthweight was associated with a lower crude abdominal fat mass, but a higher proportion of total fat mass placed abdominally.

The impact of recombinant parathyroid hormone on malignancies and mortality: 7 years of experience based on nationwide Danish registers

We used Danish registers to identify patients with osteoporosis, who had been treated with parathyroid hormone and evaluated the probability of developing cancer. We did not find an increased risk of cancer among the patients treated with parathyroid hormone.

INTRODUCTION

We evaluated the incidences of malignancies and mortality in osteoporotic patients treated with rPTH.

METHODS

Using Danish nationwide registers, we identified patients diagnosed with osteoporosis in the period 1995 through 2010. Each patient treated with rPTH ("case") was compared with 10 gender- and age-matched patients who did also have osteoporosis but did not receive rPTH ("control").

RESULTS

A total of 4,104 cases (80.3 % females) were identified. The mean age at the beginning of rPTH treatment was 70.9 (SD 9.7) years. During a follow-up time of 10,118 person-years for the cases and 88,005 person-years for the controls, a total of 255 cases (6.2 %) compared with 2,103 controls (5.1 %) experienced a cancer (Chi square, p = 0.003). We found an adjusted cancer related HR of 1.1 (95 %CI 0.9-1.4) among the cases. Lung cancer was the only cancer type with a significantly increased rate among patients receiving rPTH (HR 1.7; 95 % CI 1.3-2.3). No cases developed osteosarcomas and nine controls developed osteosarcoma. During follow-up, 627 (15.3 %) cases died and 4,175 (10.2 %) controls died, which yielded an excess mortality risk of 26 % (95 % CI 16-37 %). This could be due to differences in the prevalence of vertebral fractures between the rPTH-treated and non-treated patients.

CONCLUSION

This study did not support the hypothesis describing a possible link between rPTH treatment and the development of cancer. We also conclude that osteosarcoma has not been diagnosed in any Danish patient receiving rPTH since the year 2003 when it was introduced on the market.

Effects of paracetamol, non-steroidal anti-inflammatory drugs, acetylsalicylic acid, and opioids on bone mineral density and risk of fracture: results of the Danish Osteoporosis Prevention Study (DOPS)

Pain medication has been associated with fractures. We found higher weight in paracetamol and non-steroidal anti-inflammatory drugs (NSAID) users and lower vitamin D levels in opioid and acetylsalicylic acid users. None of the pain medications influenced bone mineral density or loss. NSAID were associated with an increased fracture risk.

INTRODUCTION

To study the effects of use of paracetamol, non-steroidal anti-inflammatory drugs (NSAID), acetylsalicylic acid (ASA), and opioids on bone mineral density (BMD) and risk of fractures.

METHODS

Two-thousand sixteen perimenopausal women followed for 10 years as part of a partly randomised comprehensive cohort study on hormone therapy (HT). BMD was measured at baseline and after 10 years by DXA (Hologic).

RESULTS

Paracetamol users were heavier (70.4 ± 13.4 vs. 67.7 ± 11.9 kg, 2p < 0.01) than non-users. NSAID users were heavier (71.6 ± 15.6 vs. 67.8 ± 11.9 kg, 2p = 0.04) than non-users. ASA users had lower 25-hydroxy-vitamin D (25OHD) levels (21.9 ± 9.3 vs. 25.3 ± 12.4 ng/ml, 2p < 0.01) than non-users. Opioid users had lower 25OHD (21.4 ± 8.4 vs. 25.2 ± 12.3 ng/ml) and lower intake of vitamin D (2.2 ± 1.1 vs. 3.1 ± 3.0 μg/day, 2p < 0.01) than non-users. Despite these differences, no baseline differences were present in spine, hip, forearm or whole body BMD. Over 10 years, no differences were present in BMD alterations except a small trend towards a higher BMD gain in the spine in users of paracetamol, NSAID, ASA, and opioids compared to non-exposed. After adjustment, NSAID exposed sustained more fractures (HR = 1.44, 95% CI 1.07-1.93) than non-users. For users of paracetamol and opioids, a non-significant trend towards more fractures was present after adjustment. For ASA users, no excess risk of fractures was present.

CONCLUSION

Significant differences exist between subjects exposed to pain medications and non-users. Despite an absence of an effect over time on BMD, users of NSAID experienced more fractures than expected. The reasons for this have to be explored in further studies.

Polymorphisms of the peroxisome proliferator-activated receptor γ (PPARγ) gene are associated with osteoporosis

Stimulation of PPARγ turns mesenchymal stem cells into adipocytes instead of osteoblasts. We investigated the effect of polymorphisms in the PPARγ gene on BMD and fracture risk in two Danish cohorts and found opposing effects of certain SNPs and haplotypes in the two cohorts probably owing to environmental factors.

INTRODUCTION

Stimulation of PPARγ causes development of mesenchymal stem cells to adipocytes instead of osteoblasts leading to decreased osteoblast number and BMD. The aim of this study was to examine the effect of PPARG polymorphisms on BMD and fracture risk in two Danish cohorts: AROS, a case-control population comprising 809 individuals and DOPS, a population comprising 1,716 perimenopausal women allocated to hormone therapy or not at baseline and followed for 10 years. On the basis of linkage disequilibrium between SNPs throughout the gene and previous studies we chose 10 polymorphisms for investigation.

METHODS

In AROS, individuals heterozygous for the polymorphisms rs12497191, rs4135263, and rs1151999 had an increased risk of vertebral fractures (OR = 1.48-1.76, p = 0.005-0.04) compared with individuals homozygous for the common allele. In DOPS, individuals heterozygous for rs1151999 had an increased BMD at the hip sites (p ≤ 0.02). An interaction between rs1151999 and diet was found on BMD in both cohorts.

RESULTS

For the polymorphism rs1152003 there was an interaction with body weight on BMD at all sites in both cohorts (p ≤ 0.07). Stratified analyses revealed that in the high weight group in AROS individuals homozygous for the variant allele had a decreased BMD (p ≤ 0.02), whereas the same pattern was found in the low weight group in DOPS (p ≤ 0.03). A number of haplotype associations were found as well, the direction of which was opposite in the two cohorts.

CONCLUSION

Our study suggests an association SNPs in PPARG and haplotypes thereof and BMD and fracture risk. The effect however appears to be modifiable by environmental factors.

Polymorphisms in the ALOX12 gene and osteoporosis

ALOX12 produces ligands for PPARγ thereby turning mesenchymal stem cells into adipocytes instead of osteoblasts. We investigated the effect of polymorphisms in the ALOX12 gene on BMD and fracture risk in two Danish cohorts and found four polymorphisms and a haplotype thereof to be associated with BMD and fracture risk.

INTRODUCTION

Stimulation of the PPARγ with ligands produced by the ALOX enzymes drives mesenchymal stem cells in an adipocyte direction at the expense of osteoblasts leading to decreased osteoblast number and BMD. Previously, polymorphisms in the ALOX12 gene have been associated with osteoporosis.

METHODS

We examined the effect of ALOX12 polymorphisms on BMD and the risk of fractures in two Danish cohorts: AROS, a case-control population comprising 809 individuals and DOPS, a population comprising 1,716 perimenopausal women allocated to hormone therapy or not at baseline and followed for up to 10 years. On the basis of linkage disequilibrium (LD) between SNPs throughout the gene and previous genetic association studies we chose ten polymorphisms for investigation. Genotyping was carried out using the Sequenom MassARRAY genotyping system and TaqMan assays.

RESULTS

In AROS, individuals heterozygous for the polymorphisms rs3840880, rs9897850, rs2292350 and rs1126667 had a 3.0-4.7% decreased lumbar spine BMD (p = 0.02-0.06) and an increased risk of vertebral fractures (p < 0.05) compared with individuals homozygous for either allele. In DOPS, none of the individual SNPs were associated with BMD or incident fractures. In both cohorts, the above-mentioned SNPs comprised an LD-block (pairwise D´ = 1.0, r (2) = 0.45-0.97). A haplotype comprising all the common alleles (frequency 9%) was associated with decreased bone loss at the hip (p < 0.05) and decreased incidence of osteoporotic fractures (p < 0.05) in DOPS and increased femoral neck BMD in AROS (p < 0.05).

CONCLUSION

Our study suggests that genetic variants in ALOX12 may influence BMD and fracture risk.

Long-term high-physiological-dose growth hormone reduces intra-abdominal fat in HIV-infected patients with a neutral effect on glucose metabolism

OBJECTIVES

The aim of the study was to investigate the effect of long-term high-physiological-dose recombinant human growth hormone (rhGH) therapy on fat distribution and glucose metabolism in HIV-infected patients.

METHODS

Forty-six HIV-infected Caucasian men on highly active antiretroviral therapy (HAART), with an age range of 21-60 years and no significant comorbidity, were included in this randomized, placebo-controlled, double-blind, single-centre trial. Twenty-eight subjects were randomized to 0.7 mg/day rhGH, and 18 subjects to placebo, administered as daily subcutaneous injections between 1 and 3 pm for 40 weeks. Endpoints included changes in visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), limb fat mass, percentage of limb fat, plasma lipids, insulin resistance and glucose tolerance.

RESULTS

VAT and trunk fat mass decreased significantly in the GH group compared with the placebo group [-19 cm(2) (-11%) vs. 12 cm(2) (6%), P=0.03, and -548 g (-9%) vs. 353 g (6%), P<0.01, respectively]. The beneficial fat redistribution in the GH group occurred without concomitant changes in subcutaneous fat at the abdomen or extremities. rhGH therapy was well tolerated. Insulin resistance, glucose tolerance, and total plasma cholesterol and triglycerides did not significantly change during intervention.

CONCLUSIONS

Daily 0.7 mg rhGH treatment for 40 weeks reduced abdominal visceral fat and trunk fat mass in HIV-infected patients. This treatment appeared to be safe with respect to glucose tolerance and insulin sensitivity.

Geometry of the proximal femur in relation to age and sex: a cross-sectional study in healthy adult Danes

PURPOSE

To describe the natural variation in hip geometry in relation to Danish population characteristics, and to establish normal reference values.

MATERIAL AND METHODS

We included 249 healthy individuals (94 M and 155 F, aged 19-79 years) and measured hip-axis-length (HAL), neck-width (NW), neck-shaft-angle (NSA), and femoral head-radius (HR) on dual-energy X-ray absorptiometry (DXA) screen images.

RESULTS

HAL, NW, HR, and NSA were higher in men than in women (10.9 +/- 0.7 vs. 9.5 +/- 0.6 cm (P<0.001), 3.8 +/- 0.3 vs. 3.3 +/- 0.3 cm (P<0.01), 2.5 +/- 0.3 vs. 2.3 +/- 0.2 cm (P< 0.001), and 131 +/- 5 vs. 129 +/- 5 degrees (P< 0.01). NSA was higher in post-menopausal than in pre-menopausal women (130 +/- 4 vs. 128 +/- 5 degrees (P<0.001)). In multiple regression analysis, HAL, NW, and HR were positively related to body height in both sexes (R = 0.20 to 0.63, P<0.05 to P<0.001). In females, NSA was positively related to body height (R = 0.20, P<0.05) and negatively to body weight (R = -0.30, P<0.01). NW increased with age in men (R = 0.34, P<0.01) but not in women.

CONCLUSION

Hip dimensions differ between genders in the Danish population. HAL, NW, and HR depend on body height. Finally, NW increases with age in men but not in women.

Performance of four clinical screening tools to select peri- and early postmenopausal women for dual X-ray absorptiometry

Several methods to select postmenopausal women for dual X-ray absorptiometry (DXA) have been proposed. We decided to compare the performance of three clinical decision rules (SCORE, ORAI, OST) with the usual case-finding strategy based on the presence of a major risk factor for future fracture (CFMRF). The study subjects were 2009 healthy, white, peri- or early postmenopausal women participating in the Danish Osteoporosis Prevention Study (DOPS). DXA results expressed as T-scores and scores on SCORE, ORAI, OST and CFMRF were extracted from the DOPS database. First, we evaluated the screening tools as originally described by the developers. The resulting sensitivities and specificities ranged from 18% to 92% and from 66% to 85%, respectively. Only OST achieved a high sensitivity (92%) with respect to femoral neck T-score < or = -2.5; however, the sensitivity with respect to lumbar spine T-score < or = -2.5 was only 51%. Next, the performance of the screening tools was evaluated against T-score < or = -2.0 (and T-score < or = -2.5) in at least one of the regions: femoral neck, total hip or lumbar spine. Using ROC curve analysis, we determined cut-offs yielding sensitivities as close as possible to 90%. The CFMRF and the ORAI tool were too coarse to yield 90% sensitivity. The performances of OST and SCORE were equal from a clinical perspective in that the sensitivities and the specificities varied from 89% to 94% and from 23% to 28%, respectively. The performance of CFMRF was no better than could be expected by chance, yielding a sensitivity of 19% and a specificity of 85%. Applying SCORE or OST 75% of the women would have to be referred for densitometry to identify 90% of the women with T-score < or = -2.0 (or T-score < or = -2.5) in at least one region. In conclusion, our results question the utility of all the evaluated tools for screening peri- and early postmenopausal women for low BMD. However, if a decision on referral has to be made, it may be based on the simple OST rule, which performed as well as or better than any of the other tools.

Two single nucleotide polymorphisms in the CYP17 and COMT Genes--relation to bone mass and longitudinal bone changes in postmenopausal women with or without hormone replacement therapy. The Danish Osteoporosis Prevention Study

Sex steroids are important physiologic regulators of bone mass, and genes regulating sex steroid production and metabolism are obvious as candidate genes for osteoporosis susceptibility. We present data from a study of 1795 recent postmenopausal women, assigned to either hormone replacement therapy (HRT) or no treatment and followed for 5 years. The association between bone mass measurements and two single nucleotide polymorphisms, a T (A1) to C (A2) transition in the 5'-UTR of the cytochrome P450c17alpha (CYP17) gene and a G (Val) to A (Met) transition in exon 4 of the catechol- O-methyltransferase (COMT) gene, was evaluated. Association with CYP17 genotype was modified by body mass index (BMI). In lean women, individuals homozygous for the CYP17 A2 allele were 1 cm shorter and had lower baseline BMD (bone mineral density), BMC, and CSA (cross sectional area) in the spine and femoral neck than did other women (BMD spine A2A2: 0.975 g/cm2 versus 1.011 g/cm2 in A1A1 + A1A2, P = 0.002). Conversely, an adverse association with A2A2 and bone loss over 5 years seemed present only in overweight women, but differences were small. Response to HRT was not dependent on CYP17 genotype. COMT genotype was not associated with bone mass at baseline, bone loss in untreated women, or response to HRT. In conclusion, the A2 allele of the CYP17 T(27)-C polymorphism is associated with reduced bone mass and bone size in lean perimenopausal women, whereas high BMI protects against this negative association. The COMT G(1947)-A polymorphism is not associated with bone parameters in this study.

Polymorphisms in the CYP19 and AR genes--relation to bone mass and longitudinal bone changes in postmenopausal women with or without hormone replacement therapy: The Danish Osteoporosis Prevention Study

Polymorphisms in the androgen receptor ( AR) gene and genes encoding enzymes involved in synthesis of sex steroids (e.g., the CYP19 gene encoding aromatase) have recently received attention in osteoporosis research. In the Danish Osteoporosis Prevention Study, recent postmenopausal women were allocated to either hormone replacement therapy (HRT) or no treatment. We genotyped 1792 women for the CYP19 (TTTA)(n) repeat [short (TTTA)(n <or= 7) or long (TTTA)(n > 7)] the CYP19 C(1558)-T, and the AR (CAG)(n) repeat polymorphism [short (CAG)(n < 22), long (CAG)(n >or= 22)], and investigated associations with bone mineral density (BMD) and 5-year change in BMD. The CYP19 polymorphisms were in strong linkage disequilibrium. Perimenopausal bone mass or bone loss in untreated women was not associated with the CYP19 polymorphisms. In hormone-treated women, BMD increase in the femoral neck was highest (+0.3%/year) for long CYP19 alleles, lowest (-0.09%/year) for short alleles, and intermediate (-0.002%/year) in heterozygous women, P = 0.015. Differences were also significant in the lumbar spine, total hip, and ultradistal forearm. The C(1558)-T T-allele was associated with a more pronounced response to HRT ( P = 0.04, total hip). AR genotype was not related to BMD, but a modifying effect of sex hormone-binding globulin (SHBG) was present. In the highest SHBG quartile (SHBG > 95 nmol/1, n = 222), AR genotype was associated with baseline BMD (femoral neck: P < 0.001, total hip: P = 0.008), but without a clear gene dosage effect. We have demonstrated that polymorphisms in the CYP19 gene are associated with the magnitude of bone gain in response to HRT and that the (CAG)(n) repeat polymorphism in the AR gene is associated with bone mass in women with high levels of SHBG. These findings emphasize the complexity of the genetics of bone mass and bone loss.

Two polymorphisms in the vitamin D receptor gene--association with bone mass and 5-year change in bone mass with or without hormone-replacement therapy in postmenopausal women: the Danish Osteoporosis Prevention Study

The significance of an interrelation between nongenetic factors and genotype effects in the regulation of bone mass is not clear. In this prospective study of 429 healthy early postmenopausal Danish women, we investigated the association between bone mineral density (BMD) and the FokI and BsmI polymorphisms in the vitamin D receptor (VDR) gene. Participants were allocated to either hormone-replacement therapy (HRT) or no treatment by randomization or personal choice. After 5 years, 332 women with unchanged treatment status were available for analyses, 98 of these women were still on HRT. No association with initial BMD or 5-year change in BMD was found for either polymorphism. In women with body mass index (BMI) < 25 (n = 282), the f allele was associated with lower BMD of the hip (p < 0.001) and forearm (p = 0.001), and the b allele was associated with lower spine BMD (p = 0.02). Comparing thin/normal weight women with overweight/ obese women of the same genotype, FF women had similar BMD at all measured sites in contrast to Ff and ff women in whom BMD, as expected, was higher in the overweight/obese women. Similar results were found for the BsmI polymorphism with no difference in BMD between BMI groups in BB women. Segregation into groups according to dietary calcium intake did not reveal any genotype association with BMD. These results provide some evidence of a modifying effect of nongenetic factors, specifically BMI, on the association between VDR genotype and BMD. High BMI may protect against lower BMD seen in association with thef or b alleles. In some genotypes (FF and BB), BMI had relatively little effect on BMD.