Polymorphism in the insulin-like growth factor 1 gene is associated with age at menarche in caucasian females

Genetic determinants of age at menarche: does the LIN28B gene play a role? A narrative review

Menarche, the first menstrual period marking the onset of female reproduction, is a milestone of female puberty. The timing of menarche determines the timing of later phases of pubertal maturation in girls and has major implications for health later in life, including behavioral and psychosocial disorders during adolescence and fertility problems and increased risk for certain diseases in adulthood. Over the last few decades, a continuous decline in age at menarche has been noted, with environmental factors contributing to this change in the timing of menarche. However, a genetic component of age at menarche and pubertal onset has been strongly suggested by studies in families and twins wherein up to approximately 80% of the variance in puberty onset can be explained by heritability. Gene association studies have revealed several genetic loci involved in age at menarche, among which LIN28B has emerged as a key regulator of female growth and puberty. LIN28B, a human homolog of Lin28 of C. elegans, is a known RNA-binding protein that regulates let-7 microRNA biogenesis. Genome-wide association studies have identified the association of polymorphisms in the LIN28B gene with age at menarche in several population cohorts worldwide. In this paper, we review the genetic factors contributing to age of menarche, with particular focus on the identified polymorphisms in LIN28B gene.

Association of cigarette smoking with cerebrospinal fluid biomarkers of insulin sensitivity and neurodegeneration

INTRODUCTION

Cigarette smoking increases both the risk for insulin resistance and amyloid-β (Aβ) aggregation, and impaired brain insulin/insulin-like growth factor 1 (IGF1) signaling might increase risk factors for Alzheimer's disease (AD). We aimed to investigate the association among cerebrospinal fluid (CSF) insulin sensitivity/IGF1, glucose/lactate, and Aβ42 and further explore whether insulin sensitivity contributed to the risk for AD in active smokers.

METHODS

In this cross-sectional study, levels of insulin, IGF1, and lactate/glucose of 75 active smokers and 78 nonsmokers in CSF were measured. Three polymorphisms regulating IGF1 were genotyped. Analysis of variance was used to compare differences of variables between groups. Partial correlation was performed to test the relationship between CSF biomarkers and smoking status. General linear models were applied to test the interaction of the effect of single nucleotide polymorphisms and cigarette smoking on CSF IGF1 levels.

RESULTS

In the CSF from active smokers, IGF1 and lactate levels were significantly lower (p = .016 and p = .010, respectively), whereas Aβ42 (derived from our earlier research) and insulin levels were significantly higher (p < .001 and p = .022, respectively) as compared to the CSF from nonsmokers. The AG + GG genotype of rs6218 in active smokers had a significant effect on lower CSF IGF1 levels (p = .004) and lower CSF insulin levels in nonsmokers (p = .016).

CONCLUSIONS

Cigarette smoking as the "at-risk" factor for AD might be due to lower cerebral insulin sensitivity in CSF, and the subjects with rs6218G allele seem to be more susceptible to the neurodegenerative risks for cigarette smoking.

Association Study of IGF-1 rs35767 and rs6214 Gene Polymorphisms with Cancer Susceptibility and Circulating Levels of IGF-1, IGFBP-2, and IGFBP-3 in Colorectal Cancer Patients

Early detection of colorectal cancer (CRC) increases the 5-year survival rate by 90%; therefore, non-invasive biomarkers such as measurable circulating proteins for early detection and prognosis are crucial. Insulin-like growth factor-1 (IGF-1) is involved in the regulation of cell proliferation and apoptosis. IGF binding proteins (IGFBPs) bind and inhibit the activity of IGF-1. It was inconsistently reported that high IGF-1 and IGFBP-2 and low IGFBP-3 circulating levels are associated with high cancer risk, poor prognosis, and tumor metastasis in several cancers. A total of 175 patients with CRC and 429 controls were enrolled in this study. We genotyped for IGF-1 rs35767 and rs6214 gene polymorphisms and assessed their association with circulating levels of IGF-1 and/or the risk for CRC. We also determined plasma levels of IGF-1, IGFBP-2, and IGFBP-3. Neither rs35767 nor rs2614 were associated with cancer risk or IGF-1 levels in our study cohort. IGF-1 and IGFBP-3 levels were higher in controls than in patients, whereas IGFBP-2 was higher in patients than in controls. Only IGFBP-2 was associated with increased tumor grade but not stage. Therefore, IGF-1, IGFBP-2, and IGFBP-3 may be useful as early detection and prognostic biomarkers in CRC.

The Role of Cow's Milk Consumption in Breast Cancer Initiation and Progression

PURPOSE OF REVIEW

This review evaluates cow milk's impact on breast carcinogenesis by linking recent epidemiological evidence and new insights into the molecular signaling of milk and its constituents in breast cancer (BCa) pathogenesis.

RECENT FINDINGS

Recent prospective cohort studies support the association between cow's milk consumption and the risk of estrogen receptor-α-positive (ER⁺) BCa. Milk is a complex biological fluid that increases systemic insulin-like growth factor 1 (IGF-1), insulin and estrogen signaling, and interacting hormonal promoters of BCa. Further potential oncogenic components of commercial milk include exosomal microRNAs (miR-148a-3p, miR-21-5p), bovine meat and milk factors, aflatoxin M1, bisphenol A, pesticides, and micro- and nanoplastics. Individuals with BRCA1 loss-of-function mutations and FTO and IGF1 gain-of-function polymorphisms enhancing IGF-1/mTORC1 signaling may be at increased risk for milk-induced ER⁺ BCa. Recent prospective epidemiological and pathobiochemical studies identify commercial milk consumption as a critical risk factor of ER⁺ BCa. Large meta-analyses gathering individuals of different ethnic origins with milk derived from dairy cows of varying genetic backgrounds and diverse feeding procedures as well as missing data on thermal processing of milk (pasteurization versus ultra-heat treatment) make multi-national meta-analyses unsuitable for BCa risk estimations in susceptible populations. Future studies are required that consider all vulnerable periods of breast carcinogenesis to cow's milk exposure, beginning during the perinatal period and puberty, since these are the most critical periods of mammary gland morphogenesis. Notwithstanding the need for better studies including detailed information on milk processing and vulnerable periods of human breast carcinogenesis, the available evidence suggests that dietary guidelines on milk consumption may have to be reconsidered.

Higher Prepubertal IGF-1 Concentrations Associate to Earlier Pubertal Tempo in Both Sexes

INTRODUCTION

Pubertal onset is triggered by multiple neuroendocrine interactions. The role of prepubertal IGF-1 in this process has not been explored in both sexes. Our objective was to analyze the association of prepubertal IGF-1 concentration with age at thelarche (B2) and menarche (M) in girls and age at gonadarche (G2) in boys.

METHODS

This is a longitudinal study (n = 1,196 boys and girls) within the Growth and Obesity Chilean Cohort Study (GOCS). At age ≈ 6.7 years, blood sample was taken for IGF-1. Subjects were divided into 4 groups according to the onset age of the pubertal event.

RESULTS

Higher prepubertal IGF-1 levels were observed at earlier ages of B2 (p = 0.003) and M onset (p = 0.041). A taller prepubertal height was observed at younger ages of B2 and M (p=<0.001 and 0.002, respectively). The hazard proportional regression models (HR) showed that with an increase of 1 SD in IGF-1, the HR of presenting B2 at younger ages was 1.25, and this association was maintained when adjusted for confounding variables. Similarly, the HR of presenting M at earlier ages was 1.21. This association was maintained only when adjusting for body mass index but not using further confounders. In boys, prepubertal IGF-1 showed a tendency to be significantly higher in children with earlier G2 and taller height (both p < 0.001). The HR of presenting G2 at younger ages was 1.22, and this association was maintained after adjusting for confounders.

CONCLUSIONS

Higher IGF-1 levels in mid-childhood are associated with earlier puberty onset. The role of IGF-1 in the onset of puberty requires further investigation.

Association between the insulin-like growth factor 1 gene rs2195239 and rs2162679 polymorphisms and cancer risk: a meta-analysis

Background

Many epidemiological studies have suggested that insulin-like growth factor1 (IGF1) gene single-nucleotide polymorphisms (SNPs) may be associated with cancer risk. Among several commonly studied polymorphisms in IGF1 gene, rs2195239 and rs2162679 attracted many attentions. So we perform a meta-analysis to determine potential associations between IGF1 rs2195239 and rs2162679 polymorphisms and cancer risk.

Methods

We retrieved relevant articles from the PubMed, Embase, and Web of Science databases up to April 30, 2018. Ultimately, thirteen studies were included in the present meta-analysis, which involved 12,515 cases and 19,651 controls. The odd ratios (ORs) and their 95% confidence intervals (CIs) were pooled to estimate the strength of the associations.

Results

rs2195239 reduces the overall cancer risk in homozygote model, as well as reducing cancer risk in Asian populations in allele, homozygote, and recessive models. No significant relationship was found between rs2195239 and breast or pancreatic cancer risk. rs2162679 reduces the overall cancer risk in allele, homozygote, dominant, and recessive models, as well as reducing cancer risk in Asian populations in allele, homozygote, and recessive models.

Conclusions

IGF1 rs2195239 and rs2162679 were associated with overall cancer risk based on present studies.

Electronic supplementary material

The online version of this article (10.1186/s12881-019-0749-3) contains supplementary material, which is available to authorized users.

The association between IGF1 Gene 3'-UTR polymorphisms and cancer risk: A Meta-analysis

BACKGROUND AND OBJECTIVE

Insulin-like growth factor 1 (IGF1) gene three prime untranslated region (3'-UTR) polymorphisms have been reported to be associated with cancer risk. However, the conclusions of the relevant studies are not consistent. The present meta-analysis evaluates the relationship between IGF1 gene 3'-UTR polymorphisms (rs5742714, rs6214, and rs6220) and cancer risk.

METHODS

Articles regarding the relationship between IGF1 rs5742714, rs6214, and rs6220 polymorphisms and cancer risk were selected by searching the PubMed, Embase, and Web of Science databases before April 30, 2018. Altogether, we obtained 34 case-controlled studies from 20 articles, including 21,568 cases and 31,199 controls. The strength of associations was quantified using odds ratios (ORs) and the corresponding 95% confidence intervals (CIs).

RESULTS

In the present meta-analysis, no significant associations were detected between rs5742714, rs6214, and rs6220 and overall cancer risk. Thus, in stratified analyses, we found that rs6214 was associated with a significantly reduced risk of breast cancer under the allele, heterozygote, and dominant models (A vs G: OR, 0.94, 95% CI,0.88-1.00, P = .044; GA vs GG: OR, 0.88, 95% CI, 0.80-0.97, P = .012; AA + GA vs GG: OR, 0.89, 95% CI, 0.81-0.97, P = .011), as well as pancreatic cancer under the recessive model (AA vs GA + GG: OR, 0.68, 95% CI,0.53-0.87, P = .003). Also, rs6220 was associated with a significantly increased risk of breast cancer under the homozygote model (GG vs AA: OR, 1.23, 95% CI, 1.02-1.48, P = .031). In addition, rs6220 was found to increase overall cancer risk among Caucasians under the allele model (G vs A: OR, 1.06, 95% CI, 1.00-1.13, P = .043).

CONCLUSIONS

In this meta-analysis, we investigated and reviewed the relationship between IGF1 gene 3'-UTR polymorphisms (rs5742714, rs6214, and rs6220) and cancer risk based on present epidemiological studies. Further studies are needed to draw more precise conclusions in the future.

The relationship between Insulin-like Growth Factor 1, sex steroids and timing of the pubertal growth spurt

OBJECTIVE

Progress through puberty involves a complex hormonal cascade, but the individual contributions of hormones, particularly IGF-1, are unknown. We reanalysed Chard growth study data to explore the tempo of puberty based on changes in both height and hormone levels, using a novel method of growth curve analysis.

DESIGN AND SUBJECTS

Schoolboys (n = 54) and girls (n = 70) from Chard, Somerset, England, recruited in 1981 at age 8/9 and followed to age 16.

MEASUREMENTS

Every 6 months, height and Tanner stages (genitalia, breast, pubic hair) were recorded, and in a subsample (24 boys, 27 girls), blood samples were taken. Serum IGF-1, testosterone (boys) and oestradiol (girls) were measured by radioimmunoassay. Individual growth curves for each outcome were analysed using variants of the super-imposition by translation and rotation (SITAR) method, which estimates a mean curve and subject-specific random effects corresponding to size, and age and magnitude of peak velocity.

RESULTS

The SITAR models fitted the data well, explaining 99%, 65%, 86% and 47% of variance for height, IGF-1, testosterone and oestradiol, respectively, and 69-88% for the Tanner stages. During puberty, the variables all increased steeply in value in individuals, the ages at peak velocity for the different variables being highly correlated, particularly for IGF-1 vs height (r = 0·74 for girls, 0·92 for boys).

CONCLUSIONS

IGF-1, like height, the sex steroids and Tanner stages, rises steeply in individuals during puberty, with the timings of the rises tightly synchronized within individuals. This suggests that IGF-1 may play an important role in determining the timing of puberty.

Association study of TAC3 and TACR3 gene polymorphisms with idiopathic precocious puberty in Chinese girls

BACKGROUND AND AIMS

The allele variant of neurokinin B and its receptor genes were thought important in regulating the human reproductive axis in many populations. The aim of this study was to investigate whether the variances in TAC3 and TACR3 genes that encoded neurokinin B (NKB) and its receptor (NK3R), individually, were associated with idiopathic precocious puberty in Chinese girls.

METHODS

The genotyping method of polymerase chain reaction-restriction fragment length polymorphism was applied in this study; the distribution of five active single nucleon acid polymorphisms (SNPs) in TAC3 (p.G34R, p. A63P, p.Q66*, p.S99P, and a mutation on 5' UTR) and four sites in TACR3 (A29V or G, G59E, S455G, and A449S or T) genes was analyzed in 267 healthy and 186 idiopathic precocious puberty Chinese girls.

RESULTS

Among the nine active SNPs, only A63P in TAC3 gene showed statistical differences; the p value was 0.024.

CONCLUSION

A63P in TAC3 gene was statistically associated with the puberty onset time in Chinese girls.

Polymorphisms in the insulin-like growth factor axis are associated with gastrointestinal cancer

INTRODUCTION

Numerous factors influence the development of gastrointestinal (GI) cancer. The insulin-like growth factor (IGF) axis plays a role in embryonic and postnatal growth and tissue repair. Elevated levels of IGFs, low levels of IGF binding proteins (IGFBPs) and over-expression of IGF receptor (IGFR-I) were associated with several stages of cancer. Here, the prevalence of the single nucleotide polymorphisms (SNPs) rs6214 in the IGF type I (IGF-I) gene and rs6898743 in the growth hormone receptor (GHR) gene in patients with GI cancer and controls was studied.

MATERIALS & METHODS

In this Dutch case-control study, DNA isolated from blood of 1,457 GI cancer patients; 438 patients with head and neck cancer (HNC), 475 with esophageal cancer (EC) and 544 with colorectal cancer (CRC) and 1,457 matched controls, was used to determine the rs6214 and rs6898743 genotypes by polymerase chain reaction. The association between these SNPs and GI cancer, HNC, esophageal adenocarcinoma (EAC), esophageal squamous-cell carcinoma (ESCC) and proximal or distal CRC was studied. Odds ratios (ORs) with 95% confidence interval (95% CI) were calculated via unconditional logistic regression.

RESULTS

Overall for GI cancer, the ORs for SNPs rs6214 and rs6898743 were approximately 1.0 (p-value>0.05), using the most common genotypes GG as reference. An OR of 1.54 (95% CI, 1.05-2.27) was found for EC for genotype AA of rs6214. The ORs for EAC were 1.45 (95% CI, 1.04-2.01) and 1.71 (95% CI, 1.10-2.68), for genotypes GA and AA, respectively. Genotype GC of rs6898743 showed an OR of 0.47 (95% CI, 0.26-0.86) for ESCC.

CONCLUSION

The A allele of SNP rs6214 in the IGF-I gene was associated with EAC, and with HNC in women. The GC genotype of rs6898743 in the GHR gene was negatively associated with ESCC.

Genome-wide association studies of age at menarche and age at natural menopause

Genome-wide association studies (GWAS) have been successful in uncovering genetic determinants of age at menarche and age at natural menopause. To date, more than 30 novel genetic loci have been identified in GWAS for age at menarche and 17 for age at natural menopause. These findings have stimulated a plethora of follow-up studies particularly with respect to the functional characterization of these novel loci and how these results can be translated into risk prediction. However, the genetic loci identified so far account for only a small fraction of the overall heritability. This review provides an overview of the current state of our knowledge of the genetic basis of menarche and menopause timing. It emphasizes recent GWAS results and outlines strategies for discovering the missing heritability and strategies to further our understanding of the underlying molecular mechanisms of the observed genetic associations.

The polymorphism of Insulin-like growth factor-I (IGF-I) is related to osteoporosis and bone mineral density in postmenopausal population

OBJECTIVE

It has been shown that Insulin-like growth factor-1 (IGF-1) may be related with bone mineral density (BMD) or osteoporosis. But there are few evidences on the role of genetic variation of IGF-1 on the BMD or osteoporosis. We observed the relationship between polymorphisms of IGF-1(rs35767, rs2288377 and rs5742612) with osteoporosis and BMD in the postmenopausal female population in our study.

METHODS

A total of 216 postmenopausal women with a primary diagnosis of osteoporosis and 220 normal healthy women were included in the study. Genomic DNA of IGF-1 rs35767, rs2288377 and rs5742612 was extracted from the whole blood using QIAamp blood DNA mini kits (QIAGEN, Hilden, Germany) according to the methods recommended by the manufacturer.

RESULTS

We found that T allele of rs35767 had higher increased risk of osteoporosis (OR=1.34, 95%CI=1.0-1.81). Those carrying T allele of rs35767 had a significant lower BMD at L1-L4 vertebrae, femoral neck, total hip and trochanter when compared with those carrying C allele (P < 0.05). In addition, the BMD of L1-L4 vertebrae, femoral neck, total hip and trochanter decreased by 2.09%, 3.74%, 3.52% and 2.54% in women carrying T alleles compared with those carrying C alleles.

CONCLUSION

Our study suggests that polymorphism in IGF-I rs35767 was significantly associated with BMD and osteoporosis in postmenopausal female population, and polymorphism of rs35767 could be a marker for lower BMD and risk of osteoporosis.

Genetic variation and reproductive timing: African American women from the Population Architecture using Genomics and Epidemiology (PAGE) Study

Age at menarche (AM) and age at natural menopause (ANM) define the boundaries of the reproductive lifespan in women. Their timing is associated with various diseases, including cancer and cardiovascular disease. Genome-wide association studies have identified several genetic variants associated with either AM or ANM in populations of largely European or Asian descent women. The extent to which these associations generalize to diverse populations remains unknown. Therefore, we sought to replicate previously reported AM and ANM findings and to identify novel AM and ANM variants using the Metabochip (n = 161,098 SNPs) in 4,159 and 1,860 African American women, respectively, in the Women's Health Initiative (WHI) and Atherosclerosis Risk in Communities (ARIC) studies, as part of the Population Architecture using Genomics and Epidemiology (PAGE) Study. We replicated or generalized one previously identified variant for AM, rs1361108/CENPW, and two variants for ANM, rs897798/BRSK1 and rs769450/APOE, to our African American cohort. Overall, generalization of the majority of previously-identified variants for AM and ANM, including LIN28B and MCM8, was not observed in this African American sample. We identified three novel loci associated with ANM that reached significance after multiple testing correction (LDLR rs189596789, p = 5×10⁻⁰⁸; KCNQ1 rs79972789, p = 1.9×10⁻⁰⁷; COL4A3BP rs181686584, p = 2.9×10⁻⁰⁷). Our most significant AM association was upstream of RSF1, a gene implicated in ovarian and breast cancers (rs11604207, p = 1.6×10⁻⁰⁶). While most associations were identified in either AM or ANM, we did identify genes suggestively associated with both: PHACTR1 and ARHGAP42. The lack of generalization coupled with the potentially novel associations identified here emphasize the need for additional genetic discovery efforts for AM and ANM in diverse populations.

Association of ALOX12 and ALOX15 gene polymorphisms with age at menarche and natural menopause in Chinese women

OBJECTIVE

Lipoxygenase (LOX) is one of the major metabolic enzymes for arachidonic acid, which has been reported to be associated with many postmenopausal and many hormone-related diseases. In rats, selective inhibition of the LOX pathway led to defective ovulation. However, little is known about the association of the LOX-related genes with menstruation in women. In this study, we investigated the possible association of two key gene (ALOX12 and ALOX15) polymorphisms with age of menarche and menopause in Chinese women.

METHODS

Six tagging single nucleotide polymorphisms (SNPs) of ALOX12 and five SNPs of ALOX15 were genotyped. The association of single SNPs and haplotypes in two candidate genes and age at menarche (AAM) variation was tested in 401 Chinese nuclear families using the quantitative transmissing disequilibrium test. Furthermore, the association between these SNPs and haplotypes and age at natural menopause (AANM) in 710 postmenopausal Chinese women was measured.

RESULTS

Using family- and population-based statistical procedures, significant association was found between SNPs rs312462 in ALOX12 and AAM in nuclear families (P = 0.043), and three SNPs (rs2292350, rs312470, and rs312462) in ALOX12 were significantly associated with AANM in postmenopausal women (P = 0.012, P = 0.045, and P = 0.033, respectively). Haplotype analyses corroborated our single SNP results (P = 0.030). However, we failed to find a significant association between ALOX15 gene polymorphisms and AAM as well as AANM (P > 0.05).

CONCLUSIONS

Our present results suggest that genetic variations in ALOX12 are associated with both the onset and cessation of menstruation in Chinese women living in Shanghai.

Genome-wide copy number variation association analyses for age at menarche

CONTEXT

Menarche is a significant physiological event for women. Age at menarche (AAM) is a heritable trait associated with many common female diseases. The genetic basis and the mechanism for AAM are largely unknown. Copy number variation (CNV) is a common type of genetic variation underlying human complex traits. The importance of CNV to AAM variation is unclear.

OBJECTIVE

The objective of the study was to identify CNV important to AAM variation.

DESIGN

We performed the first genome-wide CNV study of AAM in 1654 Caucasian females using Affymetrix human single-nucleotide polymorphism 6.0 array. We also replicated our findings in another Chinese cohort containing 752 women.

RESULTS

We identified a CNV, variation_38399, in the 2q14.2 region, for association with AAM (P = 1.03 × 10(-3)). The CNV has two variants (one copy and two copy), with a mean AAM of 14.00 yr and 12.90 yr, respectively. Interestingly, in a Chinese sample containing 752 women, this CNV has been replicated both with a marginally significant P = 0.090 and with a same direction of effect (a lower copy number for a later AAM). The CNV is located approximately 75 kb upstream of the diazepam binding inhibitor (DBI), a gene known to regulate estrogen levels, a key factor for menarche.

CONCLUSION

Our findings for the first time identified a novel CNV and suggested the DBI-mediated endocrinological pathway as a potential mechanism for AAM regulation.

The IGF1 pathway genes and their association with age of puberty in cattle

Insulin-like growth factor I (somatomedin C) (IGF1) influences gonadotrophin-releasing hormone (GnRH) neurons during puberty, and GnRH release guides pubertal development. Therefore, genes of the IGF1 pathway are biological candidates for the identification of single-nucleotide polymorphisms (SNPs) affecting age of puberty. In a genome-wide association study, genotyped heifers were Tropical Composite (TCOMP, n = 866) or Brahman (BRAH, n = 843), with observation of age at first corpus luteum defining puberty. We examined SNPs in or near genes of the IGF1 pathway and report seven genes associated with age at puberty in cattle: IGF1R, IGFBP2, IGFBP4, PERK (HUGO symbol EIF2AK3), PIK3R1, GSK3B and IRS1. SNPs in the IGF1 receptor (IGF1R) showed the most promising associations: two SNPs were associated with puberty in TCOMP (P < 0.05) and one in BRAH (P = 0.00009). This last SNP explained 2% of the genetic variation (R(2) = 2.04%) for age of puberty in BRAH. Hence, IGF1R was examined further. Additional SNPs were genotyped, and haplotypes were analysed. To test more SNPs in this gene, four new SNPs from dbSNP were selected and genotyped. Single SNP and haploytpe analysis revealed associations with age of puberty in both breeds. There were two haplotypes of 12 IGF1R SNPs associated with puberty in BRAH (P < 0.05) and one in TCOMP (P < 0.05). One haplotype of two SNPs was associated (P < 0.01) with puberty in BRAH, but not in TCOMP. In conclusion, the IGF1 pathway appeared more relevant for age of puberty in Brahman cattle, and IGF1R showed higher significance when compared with other genes from the pathway.

Higher levels of IGF-I and adrenal androgens at age 8 years are associated with earlier age at menarche in girls

CONTEXT

Earlier age at menarche is associated with rapid infancy weight gain and childhood obesity. The role of hormone levels in mediating these associations is unclear.

OBJECTIVE

The aim of this study was to identify childhood hormone levels at age 8 yr that are associated with early menarche, independent of body size.

DESIGN, SETTINGS, AND SUBJECTS

A total of 329 girls from a prospective United Kingdom birth cohort study provided blood samples at mean age 8.1 yr (range, 8.0-8.5) for hormone measurements and were followed longitudinally to establish age at menarche.

MAIN OUTCOME MEASURES

Fasting plasma levels of IGF-I, androstenedione, dehydroepiandrosterone sulfate (DHEAS), leptin, insulin, IGF binding protein-1, and SHBG were measured. Age at menarche was reported by questionnaire and categorized as before 12.0, 12.0-13.0, or later than 13 yr.

RESULTS

Earlier menarche was associated with greater body weight, height, and body mass index at age 8 yr (all P-trend <0.001). Before adjustment for body size, earlier menarche was associated with higher levels of IGF-I, androstenedione, DHEAS, leptin, and fasting insulin, and with lower levels of IGF binding protein-1 and SHBG at age 8 yr (all P < 0.01). After adjustment for body mass index and height at age 8 yr, only IGF-I (P = 0.004), androstenedione (P = 0.01), and DHEAS (P = 0.01) remained associated with earlier menarche.

CONCLUSIONS

Associations between higher levels of IGF-I and adrenal androgens at age 8 yr with earlier menarche, independent of body size, support functional roles of these hormones in regulating puberty timing in girls. Higher levels of these hormones reported in children who exhibited rapid weight gain during infancy may indicate their role in developmental pathways leading to earlier sexual maturation.

Polymorphisms in adiposity-related genes are associated with age at menarche and menopause in breast cancer patients and healthy women

STUDY QUESTION

Is there any effect of genetic polymorphisms in adiposity-related genes on the timing of menarche and menopause and the total duration of menstruation among Korean women?

SUMMARY ANSWER

Our results suggest that the adiposity-related genes LEP, LEPR and PPARγ may play a role in the onset and cessation of menstruation, and the total duration of menstruation.

WHAT IS KNOWN AND WHAT THIS PAPER ADDS

Previous candidate-gene approaches have mainly presented the results for genes related to the estrogen metabolism pathway. Most genes of interest that participate in steroid-hormone metabolism, such as estrogen receptor α and estrogen receptor β, have been associated with age at menarche and menopause. This study shows the possibility that adiposity-related genes also influence the duration of menstruation.

PARTICIPANTS AND SETTING

We recruited 400 breast cancer patients and 452 healthy participants from a case-control study at the Center for Breast Cancer, National Cancer Center in Korea. Ten single nucleotide polymorphisms (SNPs) in the leptin (LEP), leptin receptor (LEPR) and peroxisome proliferator-activated receptor gamma (PPARγ) genes were investigated to evaluate their possible effects on menstruation. Associations between SNPs and age at menarche, age at menopause and duration of menstruation were evaluated.

MAIN RESULTS

Four SNPs (rs2167270 of LEP, rs7602 of LEPR and rs4684846 and rs3856806 of PPARγ) were associated with late menarche (≥ 17-year-old). Four SNPs (rs2167270 of LEP and rs1801282, rs2120825, and rs3856806 of PPARγ) were associated with early menopause (<40-year-old) among post-menopausal women. In logistic regression models with covariate adjustment, women with the GG genotype of rs7602 (LEPR) had a higher risk for late menarche [odds ratio (OR) = 1.83, 95% confidence interval (CI) = 1.01-3.31] compared with their counterparts carrying the GA or AA genotypes. In addition, the GG genotype of rs2167270 (LEP) was inversely associated with a duration of menstruation of <30 years (OR = 0.59, 95% CI = 0.31-1.00) compared with the GA or AA genotypes. BIAS, LIMITATIONS AND GENERALIZABILITY TO OTHER POPULATIONS: We obtained information on the age at menarche and menopause from self-administered questionnaires, and some participants might have had difficulty in remembering their age at menarche and menopause. However, this is a non-differential misclassification and should not appreciably affect the interpretation of the results of this study.

Study of leptin levels and gene polymorphisms in patients with central precocious puberty

INTRODUCTION

Three single-nucleotide polymorphisms (SNPs) in the leptin (LEP) or leptin receptor (LEPR) genes were assessed for their association with central precocious puberty (CPP).

RESULTS

The control group with the A/G SNP at LEPR 223 or A/G SNP at LEPR 109 exhibited significantly higher peak luteinizing hormone (LH) levels. The leptin level in the CPP group was significantly higher than that in the control group, but SNPs in either LEP or LEPR gene could not explain this observation.

DISCUSSION

In conclusion, SNPs at LEPR 223 and LEPR 109 were significantly associated with higher levels of LH in girls without CPP, but none of the genotypes at these SNPs were significantly associated with CPP.

METHODS

The SNP genotypes of LEP (polymorphism at promoter at nt-2548) and LEPR (223A/G, 109A/G) of 219 healthy girls and 249 girls diagnosed with CPP were compared. Allele frequencies in SNPs were compared with anthropometric measures, circulating leptin, hormones (estradiol, follicle-stimulating hormone, and LH), and lipid concentrations for CPP risk.

Genetics of age at menarche: a systematic review

BACKGROUND

Menarche is the first menstrual period of a girl at puberty. The timing of menarche is important for health in later life. Age at menarche is a complex trait and has a strong genetic component. This review summarizes the results of the genetic studies of age at menarche conducted to date, highlights existing problems in this area and outlines prospects of future studies on genetic factors for the trait.

METHODS

PubMed and Google Scholar were searched until May 2011 using the keywords: 'menarche', 'puberty' and 'age at menarche' in combination with the keywords 'polymorphism', 'candidate gene', 'genome-wide association study' and 'linkage'.

RESULTS

Our search yielded 170 papers, 35 of which were selected for further analysis. Several large-scale genome-wide association studies along with a powerful meta-analysis of their aggregated data identified about 50 candidate genes for the trait. Some genes were replicated in different studies of Caucasians (e.g. LIN28B, TMEM38B) or in different ethnicities (e.g. SPOCK, RANK and RANKL). However, despite the large volume of results obtained, there is a huge gap in relevant data on ethnic groups other than Caucasians.

CONCLUSIONS

The reviewed studies laid a solid basis for future research on genetics of age at menarche. However, as yet specific genes for this trait have not been identified consistently in all ethnicities and types of studies. We suggest expanding the research to different ethnicities and propose several methodologies to increase the efficiency of studies in this area, including a systems approach, which combines existing high-throughput methods in a single pipeline.

Association analyses suggest the effects of RANK and RANKL on age at menarche in Chinese women

OBJECTIVES

Age at menarche (AAM), the time of the first menstrual bleeding, is an important developmental milestone in the female life. It marks the beginning of the reproductive period. AAM is implicated in the risk of many health complications in later life. In this study, we conducted an analysis for association of single nucleotide polymorphisms (SNPs) and common haplotypes of two candidate genes, RANK (receptor activator of the NF-κB) and RANKL (receptor activator of the NF-κB ligand), with AAM in 825 unrelated Chinese women.

METHODS

In total, 73 SNPs of RANKL and 23 SNPs of RANK were genotyped. The SNPs and common haplotypes were then analyzed for their association with AAM. Age and age( 2 ) were used as covariates.

RESULTS

We found five individual SNPs (rs7239261, rs8094884, rs3826620, rs8089829, and rs9956850) of RANK significantly associated with AAM (p < 0.05). Although no significant association was identified for the RANKL gene, three polymorphisms showed nearly significant (0.05 < p < 0.08) association with AAM. Seven haplotypes of RANK were significantly associated with AAM (p < 0.05); the most significant association of the AT haplotype composed by rs1805034 and rs4524034 (p = 9.4 × 10(-4)) remained significant (p = 0.0235) after the Bonferroni correction for multiple testing. Three haplotypes of RANKL were significantly associated with AAM (p < 0.05). Importantly, the association of rs3826620 replicated our previous findings for Caucasian females.

CONCLUSIONS

The results of the present study suggest that the RANK and RANKL are two candidate genes for AAM in Chinese women.

IGF1R mutations as cause of SGA

Until 2003 monogenetic aberrations that lead to a child that is born too small for gestational age (SGA) were poorly defined. With the first report of mutations within the insulin-like growth factor type 1 receptor (IGF1R) gene in two non-syndromic patients born SGA, who failed to thrive despite normal or even elevated IGF1 serum concentrations the concept of IGF1 resistance has been established. The identification of additional individuals bearing IGF1R mutations along with comparative, genetic, structural and biochemical studies has provided evidence for the pathogenic impact of the IGF1R mutations on human longitudinal growth. However, the variability in the occurrence of additional clinical manifestations, such as developmental delay, might indicate that the pleiotropic functions of the IGF-IGF1R system are partially redundant. It is apparent that we have just begun to unravel the multifaceted IGF1R actions at the interface of growth control, maintenance of metabolic homeostasis and neurodevelopment and neural protection.

A large-scale candidate gene association study of age at menarche and age at natural menopause

Recent genome-wide association (GWA) studies have identified several novel genetic loci associated with age at menarche and age at natural menopause. However, the stringent significance threshold used in GWA studies potentially led to false negatives and true associations may have been overlooked. Incorporating biologically relevant information, we examined whether common genetic polymorphisms in candidate genes of nine groups of biologically plausible pathways and related phenotypes are associated with age at menarche and age at natural menopause. A total of 18,862 genotyped and imputed single nucleotide polymorphisms (SNPs) in 278 genes were assessed for their associations with these two traits among a total of 24,341 women from the Nurses' Health Study (NHS, N = 2,287) and the Women's Genome Health Study (WGHS, N = 22,054). Linear regression was used to assess the marginal association of each SNP with each phenotype. We adjusted for multiple testing within each gene to identify statistically significant SNP associations at the gene level. To evaluate the overall evidence for an excess of statistically significant gene associations over the proportion expected by chance, we applied a one-sample test of proportion to each group of candidate genes. The steroid-hormone metabolism and biosynthesis pathway was found significantly associated with both age at menarche and age at natural menopause (P = 0.040 and 0.011, respectively). In addition, the group of genes associated with precocious or delayed puberty was found significantly associated with age at menarche (P = 0.013), and the group of genes involved in premature ovarian failure with age at menopause (P = 0.025).

A population-based study of IGF axis polymorphisms and the esophageal inflammation, metaplasia, adenocarcinoma sequence

BACKGROUND & AIMS

Insulin-like growth factor (IGF) axis plays a key role in cell development, proliferation, and survival and is implicated in the etiology of several cancers. Few studies have examined the relationship between genetic variation of this axis and esophageal adenocarcinoma (EAC) or its precursors.

METHODS

In a population-based case-control study, we investigated the association of common polymorphisms of IGF-1, IGF-2, IGF-1 receptor, IGF binding protein-3, growth hormones (GH) 1 and GH2, and GH receptor with reflux esophagitis (RE), Barrett esophagus (BE), and EAC. Two hundred and thirty RE, 224 BE, 227 EAC cases, and 260 controls were studied. Gene polymorphisms were identified using publicly available online resources; 102 IGF axis tag and putatively functional single-nucleotide polymorphisms (SNPs) were analyzed using MassARRAY iPLEX and Taqman assays. Results were analyzed using Haploview.

RESULTS

Three polymorphisms were disease-associated. IGF1 SNP rs6214 was associated with BE (adjusted P = .039). Using GG genotype as reference, odds ratio for BE in AA (wild-type) was 0.43 (95% confidence interval [CI], 0.24-0.75). GH receptor SNP rs6898743 was associated with EAC (adjusted P = .0112). With GG as reference, odds ratio for EAC in CC (wild-type) genotype was 0.42 (95% CI, 0.23-0.76). IGF1 (CA)(17) 185-bp allele was associated with RE (adjusted P = .0116). Using IGF1(non17) as reference, odds ratio for RE in IGF1(17) carriers was 7.29 (95% CI, 1.57-46.7).

CONCLUSIONS

In this study, 3 polymorphisms of IGF genes were associated with EAC or its precursors. These polymorphisms may be markers of disease risk; independent validation of our findings is required. These results suggest the IGF pathway is involved in EAC development.

Heterozygous mutation within a kinase-conserved motif of the insulin-like growth factor I receptor causes intrauterine and postnatal growth retardation

BACKGROUND

IGF-I receptor (IGF1R) plays an essential role in human intrauterine and postnatal development. Few heterozygous mutations in IGF1R leading to IGF-I resistance and intrauterine and postnatal growth retardation have been described to date.

OBJECTIVE

The clinical and functional relevance of a novel heterozygous IGF1R mutation identified in a girl with short stature and six relatives was evaluated.

PATIENTS

Affected individuals showed birth lengths between -1.40 and -1.82 sd score (SDS) and birth weights between -1.84 and -2.19 SDS. Postnatal growth retardation ranged between -1.51 and -3.93 height SDS. Additional phenotypic findings were variable including microcephaly, clinodactyly, delayed menarche, and diabetes mellitus type 2. Genetic analyses were initiated due to elevated IGF-I levels of the girl.

RESULTS

Denaturing HPLC screening and direct DNA sequencing revealed a heterozygous G3464C IGF1R mutation in exon 19 located within a phylogenetically conserved motif of the kinase domain. The resultant mutation of glycine 1125 to alanine (G1125A) did not affect IGF1R protein expression in transiently transfected COS-7 cells and Igf1R deficient mouse fibroblasts but abrogated IGF-I-induced receptor autophosphorylation and phosphorylation of downstream kinases protein kinase B/Akt and MAPK/Erk (mouse proteins are reported). Cotransfection of wild-type and mutant IGF1R resulted in reduced autophosphorylation of 36 +/- 10% of wild-type levels, suggesting a partial dominant-negative effect.

CONCLUSION

The identified G1125A mutation results in a kinase-deficient IGF1R, which is likely to cause the phenotype of intrauterine and postnatal growth retardation.

Association of maternal and intrauterine characteristics with age at menarche in a multiethnic population in Hawaii

This study seeks to further elucidate the mother-daughter hormonal relationship and its effects on daughter's breast cancer risk through the association with early age at menarche. Four hundred and thirty-eight healthy girls, age 9-18 and of White, Asian, and/or Polynesian race/ethnicity, were recruited from an HMO on Oahu, Hawaii. Anthropometric measures were taken at a clinic visit, and family background questionnaires were completed. Cox proportional hazards regression was used to test the association of maternal and intrauterine hormone-related exposures with age at menarche. Weight and gestational age at birth and maternal pregnancy-induced nausea were not associated with age at menarche. Each year older of the mother's age at menarche was associated with a 21% reduced risk of an early age at menarche for the daughter (95% CI: 0.73-0.86). This association between mother's and daughter's menarcheal age was statistically significant for girls of Asian, White, and Mixed, Asian/White race/ethnicity, but not for girls of Mixed, part-Polynesian race/ethnicity (p (interaction) = 0.01). There was a suggestion that maternal history of breast cancer was associated with an increased risk of early age at menarche (HR = 2.18, 95% CI: 0.95-4.98); there was no association with second-degree family history. These findings support the hypothesis that maternal and intrauterine hormone-related exposures are associated with age at menarche.

Growth hormone dose in growth hormone-deficient adults is not associated with IGF-1 gene polymorphisms

AIMS

Several SNPs and a microsatellite cytosine-adenine repeat promoter polymorphism of the IGF-1 gene have been reported to be associated with circulating IGF-1 serum concentrations. Variance in IGF-1 concentrations due to genetic variations may affect different response to growth hormone (GH) treatment, resulting in different individually required GH-doses in GH-deficient patients. The aim of this study was to test if the IGF-1 gene polymorphisms are associated with the GH-dose of GH-deficient adults.

MATERIALS & METHODS

A total of nine tagging SNPs, five additionally selected SNPs and a cytosine-adenine repeat polymorphism were determined in 133 German adult patients (66 men, 67 women; mean age 45.4 years +/- 13.1 standard deviation; majority Caucasian) with GH-deficiency (GHD) of different origin, derived from the prospective Pfizer International Metabolic Study (KIMS) Pharmacogenetics Study. Patients received GH-treatment for 12 months with finished dose-titration of GH and centralized IGF-1 measurements. GH-dose after 1 year of treatment, IGF-1 concentrations, IGF-1-standard deviation score (SDS), the IGF-1:GH ratio and anthropometric data were analyzed by genotype.

RESULTS

Except for rs1019731, which showed a significant difference of IGF-1-SDS by genotypes (p = 0.02), all polymorphisms showed no associations with the GH-doses, IGF-1 concentrations, IGF-1-SDS and IGF-1:GH ratio after adjusting for the confounding variables gender, age and BMI.

CONCLUSION

IGF-1 gene polymorphisms were not associated with the responsiveness to exogenous GH in GHD. Therefore, genetic variations of the IGF-1 gene seem not to be major influencing factors of the GH-IGF-axis causing variable response to exogenous GH-treatment.

Genome-wide association analyses identify SPOCK as a key novel gene underlying age at menarche

For females, menarche is a most significant physiological event. Age at menarche (AAM) is a trait with high genetic determination and is associated with major complex diseases in women. However, specific genes for AAM variation are largely unknown. To identify genetic factors underlying AAM variation, a genome-wide association study (GWAS) examining about 380,000 SNPs was conducted in 477 Caucasian women. A follow-up replication study was performed to validate our major GWAS findings using two independent Caucasian cohorts with 854 siblings and 762 unrelated subjects, respectively, and one Chinese cohort of 1,387 unrelated subjects—all females. Our GWAS identified a novel gene, SPOCK (Sparc/Osteonectin, CWCV, and Kazal-like domains proteoglycan), which had seven SNPs associated with AAM with genome-wide false discovery rate (FDR) q<0.05. Six most significant SNPs of the gene were selected for validation in three independent replication cohorts. All of the six SNPs were replicated in at least one cohort. In particular, SNPs rs13357391 and rs1859345 were replicated both within and across different ethnic groups in all three cohorts, with p values of 5.09×10⁻³ and 4.37×10⁻³, respectively, in the Chinese cohort and combined p values (obtained by Fisher's method) of 5.19×10⁻⁵ and 1.02×10⁻⁴, respectively, in all three replication cohorts. Interestingly, SPOCK can inhibit activation of MMP-2 (matrix metalloproteinase-2), a key factor promoting endometrial menstrual breakdown and onset of menstrual bleeding. Our findings, together with the functional relevance, strongly supported that the SPOCK gene underlies variation of AAM.

Menarche is a physical milestone in a woman's life. Age at menarche (AAM) is related to many common female health problems. AAM is mainly determined by genetic factors. However, the specific genes and the associated mechanisms underlying AAM are largely unknown. Here, taking advantage of the most recent technological advances in the field of human genetics, we identified multiple genetic variants in a gene, SPOCK, which are associated with AAM variation in a group of Caucasian women. This association was subsequently confirmed not only in two independent groups of Caucasian women but also across ethnic boundaries in one group of Chinese women. In addition, SPOCK has a function in regulating a key factor involved in menstrual cycles, MMP-2, which provides further support to our findings. Our study provides a solid basis for further investigation of the gene, which may help to reveal the underlying mechanisms for the timing of menarche and for AAM's relationship with women's health in general.

What controls the timing of puberty? An update on progress from genetic investigation

PURPOSE OF REVIEW

Puberty is an important developmental stage during which reproductive capacity is attained. Genetic and environmental factors both influence the timing of puberty, which varies greatly among individuals. However, although genetic variation is known to influence the normal spectrum of pubertal timing, the specific genes involved remain unknown.

RECENT FINDINGS

Recent genetic analyses have identified a number of genes responsible for rare disorders of pubertal timing such as hypogonadotropic hypogonadism and Kallmann syndrome. However, although the genetic basis of population variation in the timing of puberty is an active area of investigation, no genetic loci have been reproducibly associated with pubertal timing thus far.

SUMMARY

This review provides an update of the genes implicated in disorders of puberty, discusses genes and pathways that may be involved in the timing of normal puberty, and suggests additional avenues of investigation to identify genetic regulators of puberty in the general population.

[Advances on related genes with sexual precocity in mammals]

In mammals and humans, reproductive capacity is attained at puberty as the end-point of a complex series of developmental and neuroendocrine events that lead to true sexual maturity. As for humans, sexual precocity looks like a pathologic status. While for some animals, sexual precocity may be a valuable quantitative character. For some species, the character of sexual precocity was developed in the evolutionary process and stably transmitted to future generations. Sexual precocity is a complex character determined by polygenes. This review introduced the association between KiSS-1, GPR54, LHR, FSHR, CYP, ER, TGFa, IGF-, GNAS1, HSD3B2, SHBG, VDR genes and sexual precocity in mammals.

Association studies of common variants in 10 hypogonadotropic hypogonadism genes with age at menarche

CONTEXT

Although the timing of puberty is a highly heritable trait, little is known about the genes that regulate pubertal timing in the general population. Several genes have been identified that, when mutated, cause disorders of delayed or absent puberty such as hypogonadotropic hypogonadism (HH).

OBJECTIVE

Because severe variants in HH-related genes cause a severe puberty phenotype, we hypothesized that common subtle variation in these genes could contribute to the population variation in pubertal timing.

DESIGN

We assessed common genetic variation in 10 HH-related genes in 1801 women from the Hawaii and Los Angeles Multiethnic Cohort with either early (age<11 yr) or late (age>14 yr) menarche and in other replication samples. In addition to these common variants, we also studied the most frequently reported HH mutations to assess their role in the population variation in pubertal timing. SETTING AND PATIENTS/OTHER PARTICIPANTS: Within the general community, 1801 women from the Hawaii and Los Angeles Multiethnic Cohort participated.

MAIN OUTCOME MEASURES

We assessed the association of genetic variation with age at menarche.

RESULTS

We found no significant association between any of the variants tested and age at menarche, although we cannot rule out modest effects of these variants or of other variants at long distances from the coding region. In several self-reported racial/ethnic groups represented in our study, we observed an association between estimated genetic ancestry and age at menarche.

CONCLUSIONS

Our results suggest that common variants near 10 HH-related loci do not play a substantial role in the regulation of age at menarche in the general population.

A genome-wide linkage scan for age at menarche in three populations of European descent

CONTEXT

Age at menarche (AAM) is an important trait both biologically and socially, a clearly defined event in female pubertal development, and has been associated with many clinically significant phenotypes.

OBJECTIVE

The objective of the study was to identify genetic loci influencing variation in AAM in large population-based samples from three countries.

DESIGN/PARTICIPANTS

Recalled AAM data were collected from 13,697 individuals and 4,899 pseudoindependent sister-pairs from three different populations (Australia, The Netherlands, and the United Kingdom) by mailed questionnaire or interview. Genome-wide variance components linkage analysis was implemented on each sample individually and in combination.

RESULTS

The mean, sd, and heritability of AAM across the three samples was 13.1 yr, 1.5 yr, and 0.69, respectively. No loci were detected that reached genome-wide significance in the combined analysis, but a suggestive locus was detected on chromosome 12 (logarithm of the odds = 2.0). Three loci of suggestive significance were seen in the U.K. sample on chromosomes 1, 4, and 18 (logarithm of the odds = 2.4, 2.2 and 3.2, respectively).

CONCLUSIONS

There was no evidence for common highly penetrant variants influencing AAM. Linkage and association suggest that one trait locus for AAM is located on chromosome 12, but further studies are required to replicate these results.

Pubertal development and menarche

Puberty is the developmental process that culminates in reproductive capability and is the result of a complex series of molecular and physiological events. The release of gonadotropin-releasing hormone from specialized neurons of the hypothalamus begins the hormonal cascade that causes gonadal activation and the physical changes of puberty. Several factors have been proposed to influence the activation of the hypothalamus to trigger puberty, but the involved pathways have not been fully elucidated. The recent observations that the age of pubertal onset may be lowering in American girls calls attention to the lack of knowledge of modulating factors that affect the pubertal process. Genes necessary for puberty have been found by studying persons who do not achieve puberty; such studies have provided insights into the pathways necessary for pubertal development. A multidisciplinary focus is required to elucidate the complex mechanisms involved in the initiation and progression of puberty.

Polymorphisms in the IGF1 and IGF1R genes and children born small for gestational age: results of large population studies

Small for gestational age (SGA) is the term used to describe a group of children born with a birth weight and/or birth length below the normal range of a reference population, corrected for their gestational age. Although animal models have shown that insulin-like growth factor 1 (IGF1) and insulin-like growth factor 1 receptor (IGF1R) genes are important candidates for reduced pre- and postnatal growth, only limited case reports have been published describing mutations. This might suggest that IGF1 and IGF1R are such crucial growth factors that only common genetic polymorphisms are allowed to survive. Common IGF1 and IGF1R gene polymorphisms, such as single nucleotide polymorphisms and variable number of tandem repeats, have been investigated with conflicting results with respect to SGA-related outcomes. The exact contribution of these polymorphisms to clinical practice remains to be elucidated.

A digenic combination of polymorphisms within ESR1 and ESR2 genes are associated with age at menarche in the Spanish population

In the present study, the authors look at an association of genetic variants within estrogen synthesis and signaling pathways and age at menarche (AAM) in Spanish women. They analyzed 9 polymorphisms in 6 different genes in 714 well-characterized postmenopausal women from Spain. They performed a quantitative trait locus study of these markers individually or in digenic combinations in relation to AAM. None of the studied markers, with the exception of the follicle-stimulating hormone receptor (P = .013), were significantly associated with AAM in the Spanish population, and no marker demonstrated an association of statistical significance after multiple testing corrections (P > .0055). In contrast, linear regression analysis suggests epistatic interactions including ESR1 and ESR2 loci in relation to AAM in the series (P = .003). The results suggest that epistatic interactions of ESR1 and ESR2 alleles could be associated with advancing AAM among Spanish women.