Analysis of multiple data sets reveals no association between the insulin gene variable number tandem repeat element and polycystic ovary syndrome or related traits

Pathophysiologic Mechanisms of Insulin Secretion and Signaling-Related Genes in Etiology of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a common endocrinopathy in women. PCOS is characterized by anovulation, hyperandrogenism, polycystic ovaries, insulin resistance, and obesity. Despite the finding that the genetic origin of PCOS is well demonstrated in previous twin and familial clustering studies, genes and factors that can exactly explain the PCOS pathophysiology are not known. Objective(s). In this review, we attempted to identify genes related to secretion and signaling of insulin aspects of PCOS and their physiological functions in order to explain the pathways that are regulated by these genes which can be a prominent function in PCOS predisposition. Materials and Methods. For this purpose, published articles and reviews dealing with genetic evaluation of PCOS in women from peer-reviewed journals in PubMed and Google Scholar databases were included in this review. Results. The genomic investigations in women of different populations identified many candidate genes and loci that are associated with PCOS. The most important of them are INSR, IRS1-2, MTNR1A, MTNR1B, THADA, PPAR-γ2, ADIPOQ, and CAPN10. These are mainly associated with metabolic aspects of PCOS. Conclusions. In this review, we proposed that each of these genes may interrupt specific physiological pathways by affecting them and contribute to PCOS initiation. It is clear that the role of genes involved in insulin secretion and signaling is more critical than other pathways.

Single-nucleotide polymorphism of INS, INSR, IRS1, IRS2, PPAR-G and CAPN10 genes in the pathogenesis of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common and a complex female endocrine disorder, and is one of the leading cause of female infertility. Here, we aimed to investigate the association of single-nucleotide polymorphism of INS, INSR, IRS1, IRS2, PPAR-G and CAPN10 gene in the pathogenesis of PCOS. A hospital-based, observational case-control study was carried on 169 PCOS and 169 control women in the southern region of India. Genotype was carried out by real-time polymerase chain reaction. A chi-square (χ²) test was performed and the genotypes were verified to comply with the Hardy- Weinberg equilibrium. Odds ratio and 95% confidence interval were calculated to assess the relative risk. Comparison of clinical characteristics of women with PCOS and controls reveal an increase in body mass index (BMI), luteinizing hormone / follicle stimulating hormone (LH/FSH) ratio, glucose levels, insulin, testosterone, hirsutism and antral follicular count in PCOS women. The variant rs1801278 (P = 0.002; OR = 2.88; 95% CI = 1.43, 5.80) show an association with PCOS. In the genotypic (P = 0.0002) and allelic models (P = 0.000), significance persisted even after Bonferroni correction. The genotypes of SNPs strongly influence BMI, LH, LH/FSH ratio, ovarian volume and antral follicular count in PCOS women. The study results were suggestive of a positive association between Gly972Arg of IRS1 and PCOS in the south Indian population, while INS, IRS2, PPAR-G and CAPN10 failed to show any association with PCOS in our studied population. Further studies focussing the role of IRS1 are warranted to delineate its implication towards PCOS.

Hyperandrogenemia in women with polycystic ovary syndrome: prevalence, characteristics and association with body mass index

BACKGROUND

Hyperandrogenemia is one of the major diagnostic features for the diagnosis of polycystic ovary syndrome (PCOS). The aim of this study was to estimate the prevalence and the characteristics of hyperandrogenemia in women with PCOS and to investigate the association of clinical and biochemical characteristics with body mass index (BMI) according to the presence of hyperandrogenemia.

MATERIALS AND METHODS

We studied 266 women diagnosed with PCOS. Hyperandrogenemia was defined by testosterone (T) and/or free testosterone (FT) and/or ∆4 androstenedione (Δ4-A) higher than 75% of the upper limits of each hormone. Patients were stratified in two groups according to a BMI threshold of 25 kg/m2.

RESULTS

Hyperandrogenemia was present in 78.2% of the patients. Elevated levels of T were found in 58.4%, while elevated levels of FT and Δ4-A were found in 42.5% and 34.1% of patients. In normal weight women (BMI≤25 kg/m2) with hyperandrogenemia lower values of hip circumference and HOMA-IR and increased levels of T, FT, Δ4-A, 17-hydroxyprogesterone (17-OHP), dehydroepiandrosterone sulfate (DHEAS), white blood cells (WBC) and neutrophils were observed compared to women without hyperandrogenemia. Also, in overweight women higher levels of T, FT, Δ4-A, 17-OHP, DHEAS and cortisol were measured, while lower thyroid-stimulating hormone (TSH) levels were comparable to women without hyperandrogenemia.

CONCLUSION

This study showed high prevalence of hyperandrogenemia in PCOS women. Women with BMI≤25 kg/m2 have significant differences in androgens, WBC, neutrophils and HOMA-IR and women with BMI≥25 kg/m2 in androgens, TSH and cortisol according to the presence or not of hyperandrogenemia.

Association of insulin gene variable number of tandem repeats regulatory polymorphism with polycystic ovary syndrome

The present meta-analysis aimed to investigate the association between insulin gene variable number of tandem repeats (INS VNTR) and polycystic ovary syndrome (PCOS). Systematic searches of electronic databases, reference lists of included articles, and the abstracts presented at related scientific societies meetings were performed. Statistical analyses were conducted using software Stata 11.0. The pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were applied. Publication bias was tested by Begg's funnel plot and Egger's regression test. A total of 9 studies including 1075 PCOS patients and 2878 controls were included in the meta-analysis. There were evidence of statistical significant association between INS VNTR and PCOS in allelic model (OR=1.25, 95% CI=1.08-1.43, P=0.002) and dominant model (OR=1.34, 95% CI=1.11-1.63, P=0.003) but not in additive model (OR=1.38, 95% CI=0.93-2.04, P=0.11) and recessive model (OR=1.26, 95% CI=0.96-1.65, P=0.09). No significant publication bias was shown by funnel plots and Egger's regression tests. In conclusion, our meta-analysis suggests that the III allele of INS VNTR is associated with increased risk of PCOS.

Lack of association of INS VNTR polymorphism with polycystic ovary syndrome: a meta-analysis

PURPOSE

An association between the INS VNTR polymorphisms and polycystic ovary syndrome (PCOS) susceptibility has been reported in previous studies, but the results were inconsistent. This study was conducted to explore this association using meta-analysis.

METHODS

PubMed, Embase, and China National Knowledge Infrastructure (CNKI) were searched according to predefined criteria for all relevant studies published up to August 2013. Four genetic models, together with odds ratios (ORs) and 95 % confidence intervals (CI), were calculated. Subgroup analyses were performed by ethnicity, anovulatory PCOS, and Hardy-Weinberg equilibrium (HWE) in the controls.

RESULTS

In total, 13 case-control studies, including 1,767 cases and 4,108 controls, were included. No significant association was detected in overall population in all models (III/III vs. I/I: OR = 1.200, 95%CI = 0.866-1.664, P=0.277; I/III vs. I/I: OR = 1.041, 95%CI = 0.880-1.232, P=0.637; III/III + I/III vs. I/I: OR = 1.191, 95%CI = 0.912-1.554, P=0.199; III/III vs. I/III + I/I: OR = 1.100, 95%CI = 0.816-1.484, P=0.531), the same as in Caucasian and Asian populations. When the studies were limited to conform to HWE, the results remained persistent and robust. The anovulation subgroup showed significantly elevated risk in the I/III vs. I/I (OR = 1.460, 95%CI = 1.017-2.095, P=0.040).

CONCLUSIONS

This meta-analysis revealed no significant association between INS VNTR polymorphisms and the risk of PCOS in the overall population, while it supported that variance may be associated with susceptibility to PCOS with anovulation. Further confirmation is needed from more well-designed and larger studies.

Polycystic ovary syndrome, insulin resistance, and obesity: navigating the pathophysiologic labyrinth

Polycystic ovary syndrome (PCOS) is a highly prevalent endocrine-metabolic disorder that implies various severe consequences to female health, including alarming rates of infertility. Although its exact etiology remains elusive, it is known to feature several hormonal disturbances, including hyperandrogenemia, insulin resistance (IR), and hyperinsulinemia. Insulin appears to disrupt all components of the hypothalamus-hypophysis-ovary axis, and ovarian tissue insulin resistance results in impaired metabolic signaling but intact mitogenic and steroidogenic activity, favoring hyperandrogenemia, which appears to be the main culprit of the clinical picture in PCOS. In turn, androgens may lead back to IR by increasing levels of free fatty acids and modifying muscle tissue composition and functionality, perpetuating this IR-hyperinsulinemia-hyperandrogenemia cycle. Nonobese women with PCOS showcase several differential features, with unique biochemical and hormonal profiles. Nevertheless, lean and obese patients have chronic inflammation mediating the long term cardiometabolic complications and comorbidities observed in women with PCOS, including dyslipidemia, metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. Given these severe implications, it is important to thoroughly understand the pathophysiologic interconnections underlying PCOS, in order to provide superior therapeutic strategies and warrant improved quality of life to women with this syndrome.

Genetics of the polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a highly complex endocrine disorder, characterized by hyperandrogenemia, menstrual irregularities and polycystic ovaries. A strong genetic component to the etiology of PCOS is evident. However, due to the genetic and phenotypic heterogeneity of PCOS and the lack of insufficiently large cohorts, studies to identify specific contributing genes to date have yielded only few conclusive results. In this review we discuss the current status of the genetic analysis of PCOS including the results of numerous association studies with candidate genes involved in TGF-β and insulin signaling, type 2 diabetes mellitus and obesity susceptibility. Furthermore, we address current challenges in genetic studies of PCOS, and the promise of new approaches, including genome-wide association studies and next-generation sequencing.

Genetic variants associated with insulin signaling and glucose homeostasis in the pathogenesis of insulin resistance in polycystic ovary syndrome: a systematic review

BACKGROUND

Polycystic ovary syndrome must be recognized as a serious issue due to its implication on long term health regardless of an individual's age. PCOS and insulin resistance are interlinked, as approximately 40 % of women with PCOS are insulin resistant. However, the detailed molecular basis for insulin resistance that is coupled with PCOS remains poorly understood.

OBJECTIVE

To review the published evidence that polymorphisms in genes that are involved in insulin secretion and action are associated with an increased risk of PCOS.

METHODS

We reviewed articles published through November 2012 which concerned polymorphisms of genes related to insulin signaling and glucose homeostasis as well as their associations with PCOS. The articles were identified via Medline searches.

CONCLUSIONS

No consistent evidence emerged of a strong association between the risk of PCOS and any known gene that is related to insulin signaling and glucose homeostasis. Moreover, recent genome-wide association studies are inconsistent in identifying the associations between PCOS and insulin metabolism genes. Many of the studies reviewed were limited by heterogeneity in the PCOS diagnosis and by not have having a sufficient number of study participants. Further studies are warranted to determine predisposing risk factors which could modify environmental factors and thus reduce the risk of PCOS. Large genome-wide association studies devoted solely to PCOS will be necessary to identify new candidate genes and proteins that are involved in PCOS risk.

Association between INS-VNTR polymorphism and polycystic ovary syndrome in a Korean population

Polycystic ovary syndrome (PCOS) is a common disorder in women of reproductive ages. But its etiology is not fully understood yet. Variability in the number of tandem repeats of the insulin gene (INS-VNTR) is known to associate with PCOS, and it is associated with an increased risk of diabetes mellitus and other cardiovascular diseases. The aim of our study was to analyze an association between the INS-VNTR polymorphism and PCOS in a Korean population. The -23/Hph I polymorphism was used as a surrogate marker for INS-VNTR polymorphism and a total of 218 PCOS patient and 141 control DNAs were analyzed by restriction fragment length polymorphism method. Statistical analysis of genotyping results were performed using HapAnalyzer. χ² test and logistic regression were used to analyze the association between two groups. A p value <0.05 was considered statistically significant. The frequencies of A/A and A/T genotypes indicated a similar change between PCOS patients and controls. In conclusion, there was no association between PCOS and INS-VNTR polymorphism (p = 0.0544, odds ratio = 1.69). Our present data demonstrate that INS-VNTR polymorphism is not related with PCOS in Korean women. Thus, it is suggested that INS-VNTR polymorphism is not a key factor in the etiology and the pathogenesis of PCOS in a Korean population.

The link between polycystic ovary syndrome and both Type 1 and Type 2 diabetes mellitus: what do we know today?

Polycystic ovary syndrome (PCOS) and Type 2 diabetes mellitus (T2D) are both obesity-related conditions that share epidemiological and pathophysiological factors. Insulin resistance is a key factor whereby obesity influences the expression of each condition. However, the mechanisms by which insulin resistance contributes towards the manifestation of PCOS and T2D differ in important ways: in PCOS, compensatory hyperinsulinemia results in pleiotropic effects including co-gonadotrophic stimulation of ovarian and adrenal steroidogenesis; in T2D, insulin resistance contributes towards β-cell exhaustion and ultimately to hyposecretion of insulin with resultant dysglycemia. The link between PCOS and Type 1 diabetes mellitus is believed to implicate supraphysiological concentrations of insulin within the systemic circulation. Further progression of the obesity epidemic will ensure even greater prominence of important obesity-related conditions such as PCOS and T2D. Research to gain a clearer understanding of the mechanisms linking each condition should be a priority.

Sex steroid hormones and reproductive disorders: impact on women's health

The role of sex steroid hormones in reproductive function in women is well established. However, in the last two decades it has been shown that receptors for estrogens, progesterone and androgens are expressed in non reproductive tissue /organs (bone, brain, cardiovascular system) playing a role in their function. Therefore, it is critical to evaluate the impact of sex steroid hormones in the pathophysiology of some diseases (osteoporosis, Alzheimer, atherosclerosis). In particular, women with primary ovarian insufficiency, polycystic ovary syndrome, endometriosis and climacteric syndrome may have more health problems and therefore an hormonal treatment may be crucial for these women.

Understanding polycystic ovarian syndrome pathogenesis: an updated of its genetic aspects

Polycystic ovary syndrome (PCOS) is the most frequent cause of female infertility. It is also characterized by metabolic defects that raise the risk for cardiovascular disease. Despite the progress in the definition of the clinical aspects of the syndrome, only very few definite data are available about the ethiopathogenetic mechanisms that subtend PCOS. It is likely that the PCOS phenotype derives from the interaction between environmental and genetic factors. While environmental factors have easily been investigated, the individuation of the genetic factors seem to be more complex. Indeed, PCOS appears to be inherited as a complex, polygenic trait. Several family studies have been conducted with the aim to clarify the genetic aspects of PCOS, but their findings are often conflicting and not conclusive.Moreover, it is difficult to establish with certainty which genes are involved and their effective role in the development of the syndrome because in PCOS, genetic analysis is hampered by low fecundity, lack of a male phenotype, absence of an animal model, and dissimilarity of the diagnostic criteria used to select the patients. Since multiple biochemical pathways are implicated in PCOS pathogenesis, genes of steroid hormone metabolism, gonadotropin release and action, insulin secretion and action, adipose tissue metabolism and others have been investigated. Nevertheless, none of them seems to play a key role in the ethiopathogenesis of PCOS. This article reviews the large body of literature generated to support the presence of genetic abnormalities in PCOS women by taking in consideration the most important studies regarding PCOS candidate genes.

State of the Art Review: Emerging Therapies: The Use of Insulin Sensitizers in the Treatment of Adolescents with Polycystic Ovary Syndrome (PCOS)

PCOS, a heterogeneous disorder characterized by cystic ovarian morphology, androgen excess, and/or irregular periods, emerges during or shortly after puberty. Peri- and post-pubertal obesity, insulin resistance and consequent hyperinsulinemia are highly prevalent co-morbidities of PCOS and promote an ongoing state of excess androgen. Given the relationship of insulin to androgen excess, reduction of insulin secretion and/or improvement of its action at target tissues offer the possibility of improving the physical stigmata of androgen excess by correction of the reproductive dysfunction and preventing metabolic derangements from becoming entrenched. While lifestyle changes that concentrate on behavioral, dietary and exercise regimens should be considered as first line therapy for weight reduction and normalization of insulin levels in adolescents with PCOS, several therapeutic options are available and in wide use, including oral contraceptives, metformin, thiazolidenediones and spironolactone. Overwhelmingly, the data on the safety and efficacy of these medications derive from the adult PCOS literature. Despite the paucity of randomized control trials to adequately evaluate these modalities in adolescents, their use, particularly that of metformin, has gained popularity in the pediatric endocrine community. In this article, we present an overview of the use of insulin sensitizing medications in PCOS and review both the adult and (where available) adolescent literature, focusing specifically on the use of metformin in both mono- and combination therapy.

The Genetic Basis of the Polycystic Ovary Syndrome: A Literature Review Including Discussion of PPAR-gamma

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder of the women of reproductive age. Familial clustering of PCOS has been consistently reported suggesting that genetic factors play a role in the development of the syndrome although PCOS cases do not exhibit a clear pattern of Mendelian inheritance. It is now well established that PCOS represents a complex trait similar to type-2 diabetes and obesity, and that both inherited and environmental factors contribute to the PCOS pathogenesis. A large number of functional candidate genes have been tested for association or linkage with PCOS phenotypes with more negative than positive findings. Lack of universally accepted diagnostic criteria, difficulties in the assignment of male phenotype, obscurity in the mode of inheritance, and particularly small sample size of the study populations appear to be major limitations for the genetic studies of PCOS. In the near future, utilizing the genome-wide scan approach and the HapMap project will provide a stronger potential for the genetic analysis of the syndrome.

Replication of association of a novel insulin receptor gene polymorphism with polycystic ovary syndrome

OBJECTIVE

To evaluate association with polycystic ovary syndrome (PCOS) of 295 variants in 39 genes central to metabolic insulin signaling and glycogen synthase kinase 3β (GSK-3β) regulation, followed by replication efforts.

DESIGN

Case-control association study, with discovery and replication cohorts.

SETTING

Subjects were recruited from reproductive endocrinology clinics, and controls were recruited from communities surrounding the University of Alabama at Birmingham and Erasmus Medical Center, Rotterdam.

PATIENT(S)

A total of 273 cases with PCOS and 173 control subjects in the discovery cohort; and 526 cases and 3,585 control subjects in the replication cohort. All subjects were caucasian.

INTERVENTION(S)

Phenotypic and genotypic assessment.

MAIN OUTCOME MEASURE(S)

Detection of 295 single-nucleotide polymorphisms (SNPs), PCOS status.

RESULT(S)

Several SNPs were associated with PCOS in the discovery cohort. Four insulin receptor (INSR) SNPs and three insulin receptor substrate 2 (IRS2) SNPs associated with PCOS were genotyped in the replication cohort. One INSR SNP (rs2252673) replicated association with PCOS. The minor allele conferred increased odds of PCOS in both cohorts, independent of body mass index.

CONCLUSION(S)

A pathway-based tagging SNP approach allowed us to identify novel INSR SNPs associated with PCOS, one of which confirmed association in a large replication cohort.

Polycystic ovary syndrome: etiology, pathogenesis and diagnosis

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women of reproductive age, with a prevalence of up to 10%. Various diagnostic criteria have been proposed, generally centered around the features of hyperandrogenism and/or hyperandrogenemia, oligo-ovulation and polycystic ovarian morphology. Insulin resistance is present in a majority of cases, with compensatory hyperinsulinemia contributing to hyperandrogenism via stimulation of ovarian androgen secretion and inhibition of hepatic sex hormone-binding globulin production. Adipose tissue dysfunction has been implicated as a contributor to the insulin resistance observed in PCOS. Environmental and genetic factors also have a role in the development of PCOS. The syndrome is associated with numerous morbidities, including infertility, obstetrical complications, type 2 diabetes mellitus, cardiovascular disease, and mood and eating disorders. Despite these morbidities, PCOS may be common in our society owing to evolutionary advantages of the syndrome in ancient times, including smaller family sizes, reduced exposure to childbirth-related mortality, increased muscle mass and greater capacity to store energy. The diagnosis of PCOS hinges on establishing key features while ruling out other hyperandrogenic or oligo-ovulatory disorders. Treatment is focused on the goals of ameliorating hyperandrogenic symptoms, inducing ovulation and preventing cardiometabolic complications.

Genetic basis of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is associated with obesity and manifests with reproductive, hyperandrogenic and metabolic features. Although the etiology of PCOS is complex and incompletely understood, genetics plays an important role (heritability: ∼70%). Potential problems with studying the genetics of PCOS include the heterogeneity of the condition and associated sub-fertility. A candidate gene approach has been used in over 70 published studies on PCOS, most of which have been inadequately powered to detect a statistically meaningful association. Furthermore, these studies often fail to replicate prior published studies on the same candidate gene in different populations. The first genome-sequence variant (identified from a genome-wide association study in subjects with Type 2 diabetes mellitus) to be studied in PCOS (FTO gene) has been shown by our group to associate with susceptibility for the development of PCOS. This is the first genetic corroboration of a link between PCOS and obesity. Future directions include a genome-wide association study in PCOS.

Independent confirmation of association between metabolic phenotypes of polycystic ovary syndrome and variation in the type 6 17beta-hydroxysteroid dehydrogenase gene

CONTEXT

Few candidate genes for polycystic ovary syndrome (PCOS) are widely agreed upon largely due to lack of replication. Type 6 17beta-hydroxysteroid dehydrogenase (HSD17B6) gene expression is increased in PCOS ovarian theca. Previous genetic study of HSD17B6 reported significant association of rs898611 with PCOS risk and metabolic phenotypes.

OBJECTIVE

Our objective was to replicate association between polymorphisms in HSD17B6 and PCOS in a well-characterized replication cohort.

DESIGN

We conducted a case-control association study.

SETTING

Subjects were recruited from reproductive endocrinology clinics; controls were recruited from the surrounding communities of the University of Alabama at Birmingham and Cedars-Sinai Medical Center in Los Angeles. Genotyping occurred at Cedars-Sinai Medical Center.

PARTICIPANTS

Participants included 335 White women with PCOS and 198 White controls.

MAIN MEASUREMENTS

We assessed HSD17B6 genotype, PCOS status, and metabolic traits.

RESULTS

The minor allele of rs898611 was not associated with PCOS; however, it was associated with increased body mass index (P = 0.031), increased fasting insulin (P = 0.008), decreased fasting glucose/insulin ratio (P = 0.038), and increased homeostasis model assessment of insulin resistance (HOMA-IR) (P = 0.021). rs10459247 and rs10876920 were associated with increased fasting insulin (P = 0.031 and 0.019, respectively), and rs10876920 was also associated with increased HOMA-IR (P = 0.046). Haplotype T-A-T-C was associated with reduced fasting insulin (P = 0.046), and haplotype C-A-C-T was associated with increased body mass index (P = 0.032).

CONCLUSIONS

Although we did not replicate association between PCOS and rs898611, we replicated associations of this variant and others in HSD17B6 with metabolic traits. These replication data suggest a role for HSD17B6 in PCOS. How HSD17B6, an enzyme involved in steroid metabolism, may influence BMI and insulin resistance in PCOS remains to be determined.

No association of the insulin gene VNTR polymorphism with polycystic ovary syndrome in a Han Chinese population

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common endocrine disorder associated with an increased risk of type II diabetes mellitus. The results of previous research about the association of the VNTR polymorphism in 5-prime flanking region of the insulin (INS) gene with PCOS have been inconsistent. The present study was to investigate the association of the INS-VNTR polymorphism with PCOS in a Han Chinese population.

METHODS

The -23/HphI polymorphism as a surrogate marker of the INS-VNTR length polymorphism was genotyped by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) in 216 PCOS patients and 192 non-PCOS women as a control group. Allelic and genotypic frequencies were compared between patients and controls, and these results were analyzed in respect to clinical test data.

RESULTS

No significant differences were observed between the cases and controls groups either in allele (P = 0.996) or genotype (P = 0.802) frequencies of INS-VNTR polymorphism; Regarding anthropometric data and hormone levels, there were no significant differences between INS-VNTR genotypes in the PCOS group, as well as in the non-PCOS group.

CONCLUSION

The present study demonstrated for the first time that the INS-VNTR polymorphism is not a key risk factor for sporadic PCOS in the Han Chinese women. Further studies are needed to give a global view of this polymorphism in pathogenesis of PCOS in a large-scale sample, family-based association design or well-defined subgroups of PCOS.

Clinical spectrum of premature pubarche: links to metabolic syndrome and ovarian hyperandrogenism

Premature pubarche-defined as the appearance of pubic hair before age 8 years in girls and 9 years in boys-has been traditionally considered a benign entity. However, recent evidence supports the notion that premature pubarche in girls may be a forerunner of the metabolic syndrome, and may precede the development of clinical ovarian androgen excess in adolescence. This sequence seems to occur more frequently when premature pubarche was preceded by reduced fetal growth and followed by excessive postnatal catch-up in height and particularly in weight; hyperinsulinemia appears to be a key factor in the development of this sequence of events. In girls with premature pubarche and a history of a low birth weight, puberty tends to start earlier and to have a faster course, so that final height may be moderately reduced. In these girls, metformin therapy may reverse the progression to clinical ovarian hyperandrogenism, normalize body composition and excess visceral fat, and delay pubertal progression without attenuating linear growth and bone mineralization, suggesting that adult height may be improved. Long-term follow-up of these patients is needed to fully determine the ultimate effects of insulin sensitization as well as the maintenance of these benefits after discontinuation of therapy.

Prevalence of hyperandrogenemia in the polycystic ovary syndrome diagnosed by the National Institutes of Health 1990 criteria

OBJECTIVE

To determine the prevalence of elevated total and free T, and DHEAS, alone and in combination, in patients with polycystic ovary syndrome (PCOS).

DESIGN

Cross-sectional analysis.

SETTING

Tertiary care academic medical center.

PATIENT(S)

Seven hundred twenty patients diagnosed with PCOS according to the National Institutes of Health 1990 criteria.

INTERVENTION(S)

History, physical examination, and blood sampling.

MAIN OUTCOME MEASURE(S)

Hyperandrogenemia, defined as at least one androgen value above the 95th percentile of 98 healthy control women (i.e., total T >88 ng/dL, free T >0.75 ng/dL, and DHEAS >2,750 ng/mL).

RESULT(S)

A total of 716 subjects with PCOS were included. The overall prevalence of hyperandrogenemia in PCOS was 75.3%. Supranormal levels of free T were present in 57.6%, of total T in 33.0%, and of DHEAS in 32.7% of patients with PCOS. When assessing the prevalence of two abnormal values, the prevalence of simultaneously elevated androgens was lowest with total T and DHEAS (1.7%) and highest with total T and free T (20.4%). Altogether, simultaneous elevations in all three markers were found in 8.7% of subjects with PCOS.

CONCLUSION(S)

Approximately three-fourths of patients with PCOS diagnosed by the National Institutes of Health 1990 criteria have evidence of hyperandrogenemia; the single most predictive assay was the measurement of free T with approximately 60% of patients demonstrating supranormal levels.

Insulin Gene Polymorphism in Women with Polycystic Ovary Syndrome

Insulin resistance is one of the main characteristics of polycystic ovary syndrome (PCOS) and is probably genetically predisposed. Possible associations of variable nucleotide tandem repeat (VNTR) polymorphism of the insulin gene ( INS) with insulin resistance and PCOS in Slovene patients were investigated. A total of 117 PCOS patients and 108 age-matched female controls were genotyped for the INS VNTR polymorphism using real-time polymerase chain reaction and measurement of appropriate biochemical and clinical parameters. Serum fasting insulin ( I0) levels and the homeostasis model assessment index were significantly elevated in PCOS patients compared with controls. Class III INS VNTR alleles were significantly more frequent in the PCOS group. The interaction between body mass index and INS VNTR genotype was a significant predictor of serum I0 level. The interaction of obesity and the III/III INS VNTR genotype might be a risk factor for the development of PCOS.

Functional genetic polymorphisms and female reproductive disorders: Part I: Polycystic ovary syndrome and ovarian response

BACKGROUND

The identification of polymorphisms associated with a disease can help to elucidate its pathogenesis, and this knowledge can be used to improve prognosis for women with a particular disorder, such as polycystic ovary syndrome (PCOS). Since an altered response to ovarian stimulation is also a characteristic of the disease, further knowledge about its aetiology could help in defining the parameters that determine the response of an individual to ovarian stimulation.

METHODS

PubMed and EMBASE databases were systematically searched for gene association studies published until the end of August 2007, using search criteria relevant to PCOS and ovarian response to stimulation. Data from additional papers identified through hand searches were also included; 139 publications were reviewed.

RESULTS

Several genes involved in ovarian function and metabolism are associated with increased susceptibility to PCOS, but none is strong enough to correlate alone with susceptibility to the disease, or response to therapy. A single-nucleotide polymorphism in exon 10 of the FSH receptor (FSHR) gene, FSHR p.N680S, was consistently identified as having a significant association with ovarian response to FSH.

CONCLUSIONS

No consistent association between gene polymorphism and PCOS could be identified. The FSHR gene may play a significant role in the success of ovarian stimulation, and can be used as a marker to predict differences in FSHR function and ovarian response to FSH. Genotyping the FSHR p.N680S polymorphism may provide a means of identifying a population of poor responders before in vitro fertilization procedures are initiated.

Association of variants in the fat mass and obesity associated (FTO) gene with polycystic ovary syndrome

AIMS/HYPOTHESIS

Variants in the fat-mass and obesity-associated gene (FTO) influence susceptibility to type 2 diabetes via an effect on adiposity/obesity. Given the important role of obesity in the aetiology of both polycystic ovary syndrome (PCOS) and type 2 diabetes mellitus, our aim was to establish whether FTO variants are also implicated in PCOS susceptibility.

METHODS

We performed a genetic association study of FTO variant rs9939609 using case-control analyses, conducted in 463 PCOS patients (geometric mean BMI 27.5 kg/m(2)) and 1,336 female controls (geometric mean BMI 25.3 kg/m(2)) of UK British/Irish origin. We also sought evidence for associations between FTO variation and circulating testosterone levels in 324 UK PCOS patients and 1,000 women from the Northern Finland Birth Cohort of 1966. Outcome measures included FTO rs9939609 genotype frequencies by participant group and androgen measures (testosterone, free androgen index) by genotype.

RESULTS

There was a significant association between FTO genotype and PCOS status in the UK case-control analysis, which was attenuated by adjustment for BMI (Cochran-Armitage test, odds ratio [per minor allele copy] 1.30 [95% CI 1.12, 1.51], p = 7.2 x 10(-4) [unadjusted], p = 2.9 x 10(-3) [adjusted]). This association was most evident in obese PCOS patients (PCOS patients below median BMI vs UK controls, p = 0.11; above median BMI vs controls, p = 2.9 x 10(-4)). No relationship between FTO genotype and androgen levels was seen.

CONCLUSIONS/INTERPRETATION

We provide the first evidence that variants that predispose to common obesity also result in altered susceptibility to PCOS, confirming the mechanistic link between these conditions. The predominant effect of FTO variants on PCOS susceptibility is probably mediated through adiposity.

Identification of SNPs, or mutations in sequence chromatograms

With the completion of the human genome sequencing project in 2001, the identification of novel markers is rapidly gaining importance. It is increasingly recognized that SNPs (single nucleotide polymorphisms) are good markers for disease susceptibility. SNPs are DNA sequence variations that occur when a single nucleotide in the genome sequence is altered in at least 1 % of the population. SNPs may have no effect on cell function, but scientists believe that they could predispose people to disease or influence their response to a drug. This chapter describes the method of using fluorescent based sequencing to detect SNPs and mutations. Sequencing provides information on the type and location of the SNPs with high accuracy. Researchers will need to provide information on the area of the genome they wish to sequence to design primers to PCR amplify the specific region.

Disparate genetic influences on polycystic ovary syndrome (PCOS) and type 2 diabetes revealed by a lack of association between common variants within the TCF7L2 gene and PCOS

AIMS/HYPOTHESIS

Common variants of the gene encoding transcription factor 7-like 2 (TCF7L2) have a powerful effect on individual risk of type 2 diabetes (per allele odds ratio approximately 1.35). Polycystic ovary syndrome (PCOS) and type 2 diabetes are familial conditions sharing common features. Based on this, the aim of the present study was to establish whether variation in TCF7L2 also influences the development of PCOS.

METHODS

We conducted a genetic association study of variants of TCF7L2 (rs7903146 and rs12255372) using both case-control and quantitative trait approaches. Case-control analyses were conducted in (1) 369 PCOS cases and 2574 controls of UK British/Irish origin, and (2) 540 women with PCOS symptoms and 1083 controls from the Northern Finland Birth Cohort of 1966. Quantitative trait analyses (androgen levels) were also performed (1249 individuals).

RESULTS

There was no association between rs7903146 and PCOS in the UK case-control study (Cochran-Armitage test, p = 0.51); nor with symptomatic status in the Finnish cohort (p = 0.36). In addition, there were no relationships between the TCF7L2 single nucleotide polymorphism rs7903146 and androgen levels (UK cases, p = 0.99; Finnish controls, p = 0.57; Finnish symptomatic cases, p = 0.80). Results at rs12255372 were similar, reflecting strong linkage disequilibrium with rs7903146.

CONCLUSIONS/INTERPRETATION

Our study was powered to detect an effect on PCOS susceptibility similar to that previously reported for these variants on type 2 diabetes. Failure to detect any evident association with PCOS provides the strongest evidence yet that the genetic architecture of these related conditions is qualitatively distinct.

Low-density lipoprotein receptor-related protein-5 C/T polymorphism in exon 18 is associated with C peptide and proinsulin levels in control women and patients with polycystic ovary syndrome

OBJECTIVE

To assess the previously unstudied potential role of C/T (A1330V) polymorphism of the low-density lipoprotein receptor-related protein-5 gene in insulin sensitivity and secretion in polycystic ovary syndrome. The low-density lipoprotein receptor-related protein-5 gene has been found to play a role in determining insulin secretion in animal models.

DESIGN

Case-control study.

SETTING

Tertiary outpatient clinic.

PATIENT(S)

Women with polycystic ovary syndrome (n = 299; age, 27.5 +/- 7.1 y [mean +/- SD]), according to the European Society of Human Reproduction and Embryology criteria, as well as healthy control women (n = 187, age, 28.9 +/- 9.8 y).

INTERVENTION(S)

Oral glucose tolerance test, blood sampling.

MAIN OUTCOME MEASURE(S)

Glucose, insulin, C peptide, proinsulin during oral glucose tolerance tests, and lipids. Genotyping of C/T (A1330V) polymorphism by polymerase chain reaction-restriction fragment length polymorphism.

RESULT(S)

There was no difference in the frequency of genotypes between women with polycystic ovary syndrome (CC/CT/TT: 80.3%, 18.4%, 1.3%) and the control women (79.1%, 19.8%, and 1.1%). Carriers of the T allele had statistically significantly higher basal and stimulated C peptide and proinsulin levels than CC homozygotes, both basally and at the 180th minute. Regarding insulin sensitivity, there was no difference between T carriers and CC homozygotes.

CONCLUSION(S)

Polymorphism of C/T in the low-density lipoprotein receptor-related protein-5 gene is associated with C-peptide and proinsulin secretion but does not influence insulin sensitivity in either healthy women or women with polycystic ovary syndrome.

Polycystic ovarian syndrome in adolescents

PURPOSE OF REVIEW

As polycystic ovarian syndrome is among the most common endocrinologic disorders during adolescence, there is always a need to investigate all new relevant data.

RECENT FINDINGS

The present review article, is occupied with - apart from basic knowledge on polycystic ovarian syndrome - issues concerning genetics, new trends in diagnosis, and data on metabolic and endocrine features of the syndrome. Finally, emphasis is given to current therapeutic trends.

SUMMARY

Early recognition and prompt treatment of polycystic ovarian syndrome in adolescents is important to prevent long-term sequellae. More research is necessary in order to find answers to many clinical and theoretical aspects of the syndrome.

Increased prevalence of VNTR III of the insulin gene in women with gestational diabetes mellitus (GDM)

OBJECTIVE

The VNTR polymorphism in the promoter region of the insulin gene (INS-VNTR) affects transcription rate and has been associated with insulin resistance and DM2. Gestational diabetes mellitus (GDM) is a multifactorial disorder, where both impaired insulin secretion and action may be involved. The aim of the study was to examine the distribution of the INS-VNTRs in women with GDM and to investigate possible associations with features of beta cell function and glycaemic control in this population.

METHODS

One hundred and sixty-one women with GDM and 111 normal pregnant women (n) were genotyped for INS-VNTR during the 24th-32nd pregnancy week. Glucose and insulin levels were determined during the diagnostic OGTT. The majority of the previous GDM women were also examined at 3-6 months post-partum.

RESULTS

VNTR class III/III genotype was significantly more frequent in the GDM group 8.7% versus 2.7%, p=0.02 giving an OR of 3.97 (1.1-14.29). An increased frequency of the VNTR class III allele was found in those GDM women who required insulin for treatment compared to those controlled with diet alone (12.4% versus 4%, p<0.001). Basal insulin levels tended to be lower in GDM women homozygous for the class III allele without reaching statistical significance (p=0.09).

CONCLUSIONS

The INS-VNTR class III is more frequent in women who develop GDM, and may be associated with decreased ability of the beta cell to meet the increased insulin requirements as reflected by the need for insulin supplementation for adequate glycaemic control.

Genetics of polycystic ovarian syndrome

Polycystic ovarian syndrome is a complex disorder with multiple factors affecting its etiology. Elucidation of specific genes and mode of inheritance remains a significant challenge. Linkage and association studies have resulted in over 50 candidate genes as a source of heritable predisposition; however, small sample sizes and failure to reproduce results have hindered efforts. In addition, low fecundity, lack of a male phenotype, and variation of diagnostic criteria represent unique challenges to discovery of polycystic ovarian syndrome genes. A concerted effort will be necessary to conclusively rule in or rule out candidate genes.

Metabolic characteristics of women with polycystic ovaries and oligo-amenorrhoea but normal androgen levels: implications for the management of polycystic ovary syndrome

OBJECTIVE

Application of the newly introduced Rotterdam criteria for polycystic ovary syndrome (PCOS) generates four phenotypic subgroups, defined by the presence/absence of three diagnostic elements: polycystic ovarian (PCO) morphology (P); hyperandrogenism (H); and oligo-amenorrhoea (O). Whilst PCOS is associated with adverse metabolic features, the strength of the association within individual subgroups is not established. We characterized the metabolic and endocrine profiles of PCOS women who are oligomenorrhoeic but normoandrogenaemic, and compared these to other PCOS women and controls.

DESIGN

Retrospective dataset analyses.

PATIENTS

A total of 309 Europid PCOS women, all with PCO morphology, of whom 191 were also hyperandrogenaemic and oligomenorrhoeic (PHO), 76 hyperandrogenaemic with normal menses (PH) and 42 oligomenorrhoeic but normoandrogenaemic (PO); plus 76 Europid control women without PCOS.

MEASUREMENTS

Metabolic parameters: fasting insulin, lipids, homeostasis model assessment (HOMA) measures of insulin sensitivity; endocrine variables: LH, FSH; prevalence of metabolic syndrome.

RESULTS

Insulin sensitivity: PO women were indistinguishable from controls, and markedly less insulin-resistant than PHO women (vs. controls, P = 0.38 after adjustment for BMI and age; vs. PHO, P = 0.003). Metabolic syndrome: the prevalence in PO women (7.1%) was similar to that in controls (3.9%), and lower than in PHO women (29.3%, P < 0.0001). LH levels: PO women were intermediate between controls (vs. controls, P = 0.008) and PHO women (vs. PHO, P = 0.06).

CONCLUSIONS

Normoandrogenaemic, oligomenorrhoeic women with PCOS are metabolically similar to control women with significantly fewer metabolic features than PCOS women who are also hyperandrogenaemic. However, higher than normal LH and lower sex hormone-binding globulin (SHBG) concentrations in the PO women support the view that they form part of the spectrum of PCOS.

Relationship between E23K (an established type II diabetes-susceptibility variant within KCNJ11), polycystic ovary syndrome and androgen levels

Polycystic ovary syndrome (PCOS) is strongly associated with hyperinsulinaemia and type II diabetes (T2D). Sequence variation within KCNJ11 (encoding Kir6.2, the beta-cell inwardly rectifying potassium channel) is implicated in the pathogenesis of neonatal diabetes, hyperinsulinaemia of infancy and multifactorial T2D. Comprehensive tagging studies have demonstrated that the KCNJ11 E23K variant (or ABCC8 A1369S in LD>0.9) is responsible for the known association between KCNJ11 and T2D. Given the phenotypic overlap between PCOS and T2D, we investigated whether E23K is involved in susceptibility to PCOS and related traits. Case-control analyses for the KCNJ11 E23K variant were performed in (a) 374 PCOS cases and 2574 controls of UK British/Irish origin, and (b) 550 women with PCOS symptoms and 1114 controls from a Finnish birth cohort. The relationship between E23K genotype and androgen levels (a key intermediate phenotype relevant to PCOS) in 1380 samples was studied. The UK case-control analysis revealed no association between E23K genotypes and PCOS status (P=0.49; Cochran-Armitage test), and no significant relationship between E23K genotype and androgen measures in the samples for which these phenotypes were available (P=0.19). Similarly, the Finnish case-control analysis showed no association between E23K genotypes and PCOS status (P=0.75; Cochran-Armitage test), and no significant relationship between E23K genotype and androgen measures in the samples for which these phenotypes were available (Finnish controls, P=0.25; Finnish cases, P=0.08). In conclusion, these data (involving >4600 subjects) provide no evidence that common variants of the KCNJ11 E23K polymorphism have a major influence on PCOS susceptibility, though modest effect sizes (OR<1.25) cannot be excluded.

The genetics of the polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a very common endocrine disorder that has a strong genetic component and is characterized by polycystic ovaries, hyperandrogenemia, and menstrual irregularity. During the past decade, the roles of more than 70 candidate genes have been evaluated for a causal role in PCOS; however, because of genetic and phenotypic heterogeneity and underpowered studies, the results of many of these studies remain inconclusive. Here, the results of the genetic analysis of several candidate genes and gene regions-CYP11A (encoding cytochrome P450, family 11, subfamily A polypeptides), CAPN10 (encoding calpain 10), the insulin gene VNTR (variable number of tandem repeats), and D19S884 (a dinucleotide repeat marker mapping to chromosome 19p13.2)-are discussed in detail. Although past genetic studies of PCOS have yielded only modest results, resources and techniques have been assembled to remedy the major deficits of these early studies, promising that the next few years will be a very exciting and rewarding era for the genetic analysis of PCOS.

Premature adrenarche, polycystic ovary syndrome and intrauterine growth retardation: does a relationship exist?

PURPOSE OF REVIEW

Describes the origin of premature adrenarche and polycystic ovary syndrome.

RECENT FINDINGS

Growing evidence has emerged on the relationship between intrauterine growth retardation, premature adrenarche and polycystic ovary syndrome.

SUMMARY

Experimental animal research and clinical observations underline the early developmental origin of premature adrenarche and polycystic ovary syndrome. Polycystic ovaries have been noted in girls before the onset of puberty which supports the suggestion that the origin of the syndrome depends on programming of the ovary in utero. Androgens during fetal life may initially be responsible for the programming of the ovary eventually leading to polycystic ovary syndrome. In addition, the development of the syndrome is proposed to be a linear process as a result of programming of the adrenal whereby hyperandrogenaemia starting in utero, during childhood and thereafter, plays a prominent role. At the beginning of puberty androgens produced by the adrenal initiate a vicious circle characterized by neuroendocrine abnormalities partly related to androgen-dependent decreases in gonadotropin-releasing hormone pulse generator sensitivity to the negative feedback actions of ovarian steroids. This promotes the progression towards the adult polycystic ovary syndrome phenotype.

The Pregnancy in Polycystic Ovary Syndrome study: baseline characteristics of the randomized cohort including racial effects

OBJECTIVE

To report the baseline characteristics and racial differences in the polycystic ovary syndrome (PCOS) phenotype from a large multicenter clinical trial (PPCOS).

DESIGN

Double-blind, randomized trial of three treatment regimens (with extended release metformin or clomiphene citrate).

SETTING

Academic medical centers.

PATIENT(S)

Six hundred twenty-six infertile women with PCOS, aged 18-39 years, with elevated T levels and oligomenorrhea (exclusion of secondary causes), seeking pregnancy, with > or = 1 patent fallopian tube, normal uterine cavity, and a partner with sperm concentration > or = 20 x 10(6)/mL in > or = 1 ejaculate.

INTERVENTION(S)

Baseline characterization.

MAIN OUTCOME MEASURE(S)

Historical, biometric, and biochemical measures of PCOS.

RESULT(S)

There were no significant differences in baseline variables between treatment groups. The overall mean (+/-SD) age of the subjects was 28.1 +/- 4.0 years, and the mean body mass index was 35.2 kg/m2 (+/-8.7). Polycystic ovaries (PCOs) were present in 90.3% of the subjects, and the mean volume of each ovary was 10 cm3 or more. Of the subjects, 7% had ovaries that were discordant for PCO morphology. At baseline, 18.3% of the subjects had an abnormal fasting glucose level (> 100 mg/dL). Asians tended to have a milder phenotype, and whites and African Americans were similar in these measures.

CONCLUSION(S)

The treatment groups were well matched for baseline parameters, and we have added further information to the PCOS phenotype.

Genetic and environmental origins of obesity relevant to reproduction

Obesity has a negative impact on reproductive health, particularly in women with polycystic ovarian syndrome (PCOS). Obesity itself is the product of both genetic and environmental influences, although the current 'epidemic' of obesity is largely related to changes in diet and lifestyle. Single gene defects leading to obesity and disordered reproductive function are rare but can are informative about metabolic pathways involved in appetite regulation. There is good evidence that PCOS has an important genetic background, which probably involves the interaction of several genes. The phenotype of PCOS and its impact on reproductive function is profoundly affected by obesity, which, in turn has both genetic and environmental influences. Understanding the genetic basis of PCOS is important but improvements in diet and lifestyle are the best means of improving reproductive function.

Candidate genes in women with polycystic ovary syndrome

There is plentiful evidence that genetic factors have an important part to play in the etiology of polycystic ovary syndrome. As yet, however, none of the potential candidate loci have withstood the scrutiny of large case-control studies, although studies of a locus close to the insulin receptor gene on chromosome 19p are emerging as promising.

Variants implicated in cortisone reductase deficiency do not contribute to susceptibility to common forms of polycystic ovary syndrome

OBJECTIVE

There are close phenotypic similarities between cortisone reductase deficiency (CRD), a rare abnormality of cortisone metabolism, and polycystic ovary syndrome (PCOS). As there is evidence that CRD results from digenic mutations involving the genes encoding 11beta-hydroxysteroid dehydrogenase type 1 (HSD11B1) and hexose-6-phosphate dehydrogenase (H6PD), we sought to establish whether CRD-associated variants in these genes, individually or in combination, influence susceptibility to PCOS.

DESIGN

Case-control, family-based association and quantitative-trait analyses.

PATIENTS

A UK case sample comprising 256 nuclear families ascertained from a PCOS offspring and 213 singleton PCOS cases plus 549 control subjects.

MEASUREMENTS

All subjects were genotyped for CRD-related variants in HSD11B1 (rs12086634) and H6PD (rs6688832). Testosterone was measured with an in-house radioimmunoassay using ether extraction and dextran-coated charcoal separation.

RESULTS

Case-control analyses revealed no differences in genotype distribution between PCOS and controls for rs12086634 or rs6688832 (both P = 0.84). Three per cent of cases and 2.4% of controls had genotype combinations (three or more variant alleles at the two sites) considered characteristic of CRD (P = 0.73). There were no departures from expectation in the family-based association studies, and no significant associations between genotypes (individually or in combination) and BMI, WHR or testosterone.

CONCLUSIONS

The variants in HSD11B1 and H6PD typed, though implicated in causation of CRD, do not influence susceptibility to PCOS. It seems likely that additional variants within these genes are required for the development of CRD.

Heterogeneity of class I INS VNTR allele association with insulin secretion in obese children

On the basis of the near-complete linkage disequilibrium of the insulin variable number of tandem repeats ( INS VNTR) allele with the neighboring −23Hph1 A/T single-nucleotide polymorphism, previous studies have documented the association of class I (“short”) and class III (“long”) INS VNTR alleles with metabolic parameters, including circulating insulin levels. Using a new method to sequence class I alleles, we revisited this association in 346 obese children. Class I alleles are made of several types of repeats, whose repartition determines subclasses IC and ID. Fasting insulin was found to be higher in obese children with ID/ID genotypes (135 ± 12 pmol/l, n = 64) than with ID/IC or IC/IC genotypes (91 ± 5 pmol/l, n = 97, P = 0.0005). In response to oral glucose, peak insulin levels and insulin-to-glucose area under the curve ratios were higher in ID/ID (872 ± 122 pmol/l and 109 ± 15, respectively) than in ID/IC or IC/IC patients (586 ± 42 pmol/l and 76 ± 5, P = 0.02 and P = 0.04, respectively). Fasting and postglucose insulin levels were comparable in carriers of IC and of class III alleles. Our results support that the molecular structure of the VNTR allele, not only its overall length, is associated with variations of insulin secretion. ID/ID homozygosity appears responsible for the increased insulin levels previously attributed to the whole class I VNTR group. It will be important to test the ramifications of this observation for class I association with Type 1 (susceptibility) and Type 2 diabetes (protection).

Genomic variants in polycystic ovary syndrome

The polycystic ovary syndrome (PCOS) is a common disorder in premenopausal women, characterized by the presence, among other traits, of hyperandrogenism, insulin resistance, and hyperinsulinism. The familial aggregation of PCOS lead the interest to the molecular genetic basis of this syndrome, especially to the genes encoding proteins involved in androgen synthesis and the regulation of insulin synthesis and action. Considering the relationship between insulin resistance and chronic inflammation, and the clustering of inflammatory markers in PCOS patients, recent studies focused on the involvement of proinflammatory genotypes on the pathogenesis of PCOS. Mounting evidence suggest at present a complex model of inheritance for PCOS, in which predisposing and protecting genomic variants interact with environmental factors such as obesity and a sedentary lifestyle, finally leading to the classic phenotype of this syndrome. Moreover, the association of hyperandrogenism, insulin resistance and chronic inflammation raised the possibility of an increase risk of cardiovascular disease in women suffering from PCOS. In the present review we will summarize the most important findings published to date regarding the molecular genetic mechanisms underlying the association of PCOS with insulin resistance and chronic inflammation, and the possible interaction of these mechanisms with environmental factors.

Pharmacogenetics in ovarian stimulation - current concepts and future options

Tailoring ovarian stimulation to the individual patient can be challenging because the ovarian response varies substantially between patients. Pharmacogenetics has emerged as a new area of research to improve the balance between desired and undesired actions of drugs, based upon the genetic predisposition of the individual patient. Clinical studies have demonstrated that the p.N680S polymorphism of the FSH-receptor gene determines the ovarian response to FSH stimulation in patients undergoing IVF. In homozygous Ser(680)/Ser(680) type women, the FSH receptor appears to be more resistant to FSH action even in normal menstrual cycles. Therefore, genotyping of patients scheduled for ovarian stimulation could be an attractive tool to individualize FSH dosing according to genetic differences in ovarian sensitivity. More clinical studies are warranted to investigate the usefulness of genotyping for the p.N680S polymorphism as a routine diagnostic test before ovarian stimulation.

Identification of a functional polymorphism of the human type 5 17beta-hydroxysteroid dehydrogenase gene associated with polycystic ovary syndrome

CONTEXT

Polycystic ovary syndrome (PCOS) is characterized by chronic hyperandrogenic anovulation and is associated with insulin resistance. Its pathogenesis is believed to be multifactorial, and abnormal gene regulation could be one contributing factor. Type 5 17beta-hydroxysteroid dehydrogenase (17beta-HSD5) appears to be the major testosterone-forming 17beta-HSD isoenzyme in females.

OBJECTIVE

Our objective was to investigate the role of a potentially activating 17beta-HSD5 gene (HSD17B5) variant in hyperandrogenism.

DESIGN AND SETTING

We conducted a case study and case-control cohort study in our General Clinical Research Center.

STUDY SUBJECTS

Subjects included a case of PCOS who had hyperthecosis associated with profound type B insulin resistance and an unusual, frankly male testosterone response to a GnRH agonist test, as well as 121 PCOS patients and 128 population controls.

INTERVENTIONS

Interventions were diagnostic.

MAIN OUTCOME MEASURES

Main outcome measures included sequencing of HSD17B5 5'-flanking region and nine exons, genotype/phenotype studies, and in vitro functional studies.

RESULTS

Our case had a previously undescribed homozygous HSD17B5 variant (G-to-A substitution) -71 bp in the promoter region. Genotyping controls showed this to be a single-nucleotide polymorphism (SNP)-71G. Luciferase activity of a SNP-71G promoter construct was significantly higher than that of the wild type, and EMSAs revealed that SNP-71G possessed significantly increased affinity to nuclear transcription factors. SNP-71G allele frequency (32.2 vs. 22.3%) and SNP-71G allele presence (53.7% vs. 38.3%) were significantly increased in PCOS (P = 0.01) [corrected] SNP-71G homozygosity tended to contribute about 20% to the plasma testosterone level.

CONCLUSIONS

SNP-71G is a functional polymorphism that may contribute to testosterone excess in a subset of PCOS patients.

Development of polycystic ovary syndrome: involvement of genetic and environmental factors

We have recently proposed that polycystic ovary syndrome (PCOS) has its origin in fetal life. This hypothesis is based on data from animal models (rhesus monkey or sheep that have been exposed prenatally to high doses of androgen) and is supported by clinical studies. It is suggested that, in human females, exposure to excess androgen, at any stage from fetal development of the ovary to the onset of puberty, leads to many of the characteristic features of PCOS, including abnormalities of luteinizing hormone secretion and insulin resistance. It is likely that, in humans with PCOS, the development of the PCOS phenotype results primarily from a genetic predisposition for the fetal ovary to hypersecrete androgen. At present, it is unclear whether the maternal environment directly influences the development of PCOS in the offspring. Maternal androgen excess is unlikely to affect the fetus, because the placenta presents an effective barrier, but metabolic disturbances during pregnancy could affect development of the syndrome in the fetus. In postnatal life, the natural history of PCOS can be further modified by factors affecting insulin secretion and/or action, most importantly, nutrition. We now have evidence for a disorder of early follicular development in the polycystic ovary that is consistent with an increased population of primordial follicles in the fetal ovary. It remains to be determined whether this phenomenon is the cause or the effect of increased exposure to androgen within the ovary. PCOS is the commonest endocrine disorder in women. It is not only a very prevalent cause of anovulatory infertility, menstrual disturbances and hirsutism, but it is also a major risk factor for the development of type 2 diabetes mellitus in later life. The aetiology of the syndrome remains uncertain but there is increasing evidence for a genetic basis. PCOS very often becomes clinically manifest during adolescence with maturation of the hypothalamic-pituitary-ovarian axis but the genesis of the syndrome may be during very early development - perhaps even in utero. In this review, this hypothesis is explored in the light of clinical, biochemical and genetic research.