Objective: Postmenopausal estradiol (E 2 ) levels vary widely between individuals and this variation is an important determinant of diseases such as osteoporosis. It has been suggested that the estrogen receptor alpha (ESR1) gene may influence peripheral E 2 levels, but the role of common sequence variations in the ESR1 gene is unclear. Methods: In 631 postmenopausal women and 528 men from the Rotterdam Study, a populationbased, prospective cohort study of individuals aged 55 years and over, ESR1 PvuII-XbaI haplotypes were determined and correlated with plasma E2 levels. Results: In women, haplotype 1 (T-A) was significantly associated with an allele-dose-dependent decrease in E 2 . After adjusting for age, body mass index, years since menopause and testosterone levels, plasma E 2 levels decreased by 1.90 pmol/l per allele copy of this haplotype (P , 0.05). Extreme genotypes, representing 23 and 27% of the population, varied by 3.93 pmol/l. No association with plasma testosterone was observed. In a subset of 446 women, no association of genotype with plasma concentrations of dehydroepiandrosterone sulfate, androstenedione or estrone was seen. In men, none of the sex hormone levels was associated with the ESR1 PvuII-XbaI haplotypes. Conclusion: We have demonstrated a role for genetic variations in the ESR1 gene in determining postmenopausal E 2 levels in women.

Extreme phosphate levels (P) have been associated with mineralization defects and increased fracture risk. Whether P within normal range is related to bone health in the general population is not well understood. To investigate the association of P with bone mineral density (BMD) and fracture risk, we assessed two population-based cohorts: the Dutch Rotterdam Study (RS-I, RS-II, RS-III; n=6791) and the US Osteoporotic Fractures in Men (MrOS; n=5425) study. The relationship of P with lumbar spine (LS) and femoral neck (FN) BMD was tested in all cohorts via linear models; fracture risk was tested in RS-I, RS-II and MrOS through Cox models, after follow-up of 8.6, 6.6 and 10.9 years, respectively. Adjustments were made for age, body mass index, smoking, serum levels of calcium, potassium, 25-hydroxyvitamin D, and estimated glomerular filtration rate (eGFR), FN-BMD, prevalent diabetes and cardiovascular disease. Additional adjustments were made for phosphate intake, parathyroid hormone, and fibroblast growth factor 23 levels in MrOS. We further stratified by eGFR. Results were pooled through study-level meta-analyses. Hazard ratios (HR) and betas (β) (from meta-analyses) are expressed per 1 mg/dL P increase. P was positively associated with fracture risk in men and women from RS and findings were replicated in MrOS (pooled HR all (95% CI): 1.47 (1.31–1.65)). P was associated with fracture risk in subjects without chronic kidney disease (CKD): all (1.44 (1.26–1.63)) and in men with CKD (1.93 (1.42–2.62)). P was inversely related to LS-BMD in men (β: −0.06 (−0.11 to −0.02)) and not to FN-BMD in either sex. In summary, serum P was positively related to fracture risk independently from BMD and phosphate intake after adjustments for potential confounders. P and LS-BMD were negatively related in men. Our findings suggest that increased P levels even within normal range might be deleterious for bone health in the normal population.

The C-variant of a T-13910C polymorphism (rs4988235; NT_022135.15:g.25316568G > A) upstream of the lactase phlorizin hydrolase (LPH) gene causes lactose intolerance. Association studies with differences in bone parameters and fracture risk have been inconclusive. The objective of this study was to examine the association of LPH rs4988235 with body height and bone parameters and calcium homeostasis in two elderly populations of Dutch Caucasians and assess interaction with vitamin D receptor (VDR) polymorphisms. Genotyping of LPH and VDR polymorphisms was performed in 6367 individuals from the Rotterdam Study and 844 from the Longitudinal Aging Study Amsterdam (LASA). Associations with age, height, weight, bone mineral density (BMD), skeletal morphometric parameters and serum vitamin D and calcium levels, and dietary calcium intake were assessed using ANOVA or analysis of covariance, and allele dose effect was assessed using linear regression analysis. Fracture risk was analyzed using Cox's proportional hazard regression analysis. Associations with body height (p ¼ 2.7 Â 10 À8 ) and vertebral area (p ¼ .048) found in the Rotterdam Study were explained by population stratification, as assessed by principal-component analyses, and disappeared after additional adjustments. No associations with femoral neck or lumbar spine BMD or with fracture risk were detected. Calcium intake and serum ionized serum calcium were significantly lower in C-homozygotes (p ¼ 9.2 Â 10 À7 , p ¼ .02, respectively). For none of the parameters studied was interaction between the T-13910C polymorphism and VDR block 5 haplotype 1 observed. We show that the C allele of the T-13910C polymorphism causing lactose intolerance is associated with lower dietary calcium intake and serum calcium levels but not with BMD or fractures. The associations observed with height and vertebral area were the result of population stratification. This demonstrates the impact of population stratification and urges researchers to carefully take this into account in genetic associations, in particular, in dietary intake-related phenotypes, of which LPH and lactose intolerance are a strong example. ß