Increased frequency of the G972R variant of the insulin receptor substrate-1 (irs-1) gene among girls with a history of precocious pubarche

Premature adrenarche: etiology, clinical findings, and consequences

Adrenarche means the morphological and functional change of the adrenal cortex leading to increasing production of adrenal androgen precursors (AAPs) in mid childhood, typically at around 5-8 years of age in humans. The AAPs dehydroepiandrosterone (DHEA) and its sulfate conjugate (DHEAS) are the best serum markers of adrenal androgen (AA) secretion and adrenarche. Normal ACTH secretion and action are needed for adrenarche, but additional inherent and exogenous factors regulate AA secretion. Inter-individual variation in the timing of adrenarche and serum concentrations of DHEA(S) in adolescence and adulthood are remarkable. Premature adrenarche (PA) is defined as the appearance of clinical signs of androgen action (pubic/axillary hair, adult type body odor, oily skin or hair, comedones, acne, accelerated statural growth) before the age of 8 years in girls or 9 years in boys associated with AAP concentrations high for the prepubertal chronological age. To accept the diagnosis of PA, central puberty, adrenocortical and gonadal sex hormone secreting tumors, congenital adrenal hyperplasia, and exogenous source of androgens need to be excluded. The individually variable peripheral conversion of circulating AAPs to biologically more active androgens (testosterone, dihydrotestosterone) and the androgen receptor activity in the target tissues are as important as the circulating AAP concentrations as determinants of androgen action. PA has gained much attention during the last decades, as it has been associated with small birth size, the metabolic and polycystic ovarian syndrome (PCOS), and thus with an increased risk for type 2 diabetes and cardiovascular diseases in later life. The aim of this review is to describe the known hormonal changes and their possible regulators in on-time and premature adrenarche, and the clinical features and possible later health problems associating with PA.

Associations of size at birth and postnatal catch-up growth status with clinical and biomedical characteristics in prepubertal girls with precocious adrenarche: preliminary results

CONTEXT

The causes of polycystic ovarian syndrome (PCOS) in girls with precocious adrenarche (PA) remain unclear.

OBJECTIVE

Our goal was to compare the clinical, biochemical, and ultrasound characteristics of girls with PA whose size at birth was appropriate for gestational age (AGA) vs those born small for gestational age (SGA). PCOS-associated metabolic and morphological correlates were examined.

DESIGN

Glucose tolerance, ACTH stimulation, and transabdominal ultrasounds were examined in 56 AGA and 31 SGA girls with PA. Bone age and hormonal profiles were determined. SGA girls were divided into 2 groups by catch-up growth (CUG) status. Subgroups were compared.

RESULTS

Chronological age, Tanner stage for pubarche, ovarian volume, and uterine volume were similar between the groups. SGA girls had lower body mass index and higher bone age-adjusted post-corticotropin cortisol. We found increased body mass index-adjusted mean serum insulin, reduced insulin sensitivity, and reduced IGF-binding protein-1 in SGA girls. Multicystic ovaries were more common in SGA girls (odds ratio [OR] = 9.69, 95% confidence interval [CI] = 3.34-28.15; P < .001). SGA girls without CUG had a higher incidence of multicystic ovaries than CUG counterparts (OR = 8.4, 95% CI = 1.4-19.3; P = .027). Being born SGA (OR = 43.4, 95% CI = 6.9-84.7; P = .001] and exaggerated 17-hydroxyprogesterone response (OR = 15.8, 95% CI = 1.7-49.8; P = .015) were associated with multicystic ovaries.

CONCLUSIONS

Significant differences in hormone levels, insulin sensitivity, and ovarian maturity were found in prepubertal girls with PA who were SGA. Longitudinal follow-up will help determine whether these factors contribute to a specific PCOS phenotype in SGA girls with PA.

Study of association of IRS-1 and IRS-2 genes polymorphisms with clinical and metabolic features in women with polycystic ovary syndrome. Is there an impact?

OBJECTIVE

Insulin receptor substrate (IRS) proteins are critical to signal transduction in insulin target tissues. The present study was undertaken to determine whether IRS-1 Gly972Arg and IRS-2 Gly1057Asp influence hormonal and metabolic characteristics in Greek patients with polycystic ovary syndrome (PCOS) and controls.

MATERIAL AND METHODS

One hundred and eighty-three women with PCOS and 88 healthy volunteers were enrolled. Venous blood samples were obtained for genetic study and hormonal profile, glucose, and insulin assays, on days 3 to 7 from cycling patients. DNA was extracted by whole blood samples for genotyping and detection of IRS-1 Gly972Arg and IRS-2 Gly1057Asp polymorphisms.

RESULTS

Fifty-six women with PCOS (30.60%), whereas 12 women in the control group (13.64%) carried the IRS-1 polymorphism (p = 0.0026). No statistically significant differences in genotypes or allele frequencies for IRS-2 polymorphism were observed between controls and PCOS women. No significant differences in any clinical or hormonal measures between subjects on the basis of genotype were observed, except the increased levels of fasting glucose that exhibit the carriers of the Asp allele of the IRS-2 polymorphism.

CONCLUSIONS

Only the IRS-1 polymorphism is associated with increased susceptibility to PCOS in a Greek population. These loci should not be considered as major contributors to the hormonal and metabolic phenotype of PCOS.

LRP5 in premature adrenarche and in metabolic characteristics of prepubertal children

OBJECTIVE

Premature adrenarche (PA) is associated with unfavourable metabolic characteristics. We hypothesized that genetic variation in low density lipoprotein (LDL) receptor-related protein 5 (LRP5), which is involved in Wnt signalling in the adrenal cortex and in cholesterol metabolism, plays a role in the pathogenesis of PA.

DESIGN AND PATIENTS

We performed a cross-sectional association study in 73 Finnish children with PA and 97 age- and gender-matched healthy controls.

MEASUREMENTS

LRP5 genotypes were determined by direct sequencing. Single-marker associations with clinical-metabolic characteristics, including adrenocortical function, glucose tolerance and lipid profile, were examined with age and gender as covariates.

RESULTS

Nineteen single nucleotide polymorphisms (SNPs) in LRP5 were found in the 170 children. No significant differences in the genotype distributions were observed between the PA and control groups. SNPs A1330V and N740N were associated with higher serum dehydroepiandrosterone sulphate (DHEAS) levels in the control subjects (A/A vs. A/a; mean 0.8 vs. 1.4 micromol/l, P = 0.01). They were also associated with higher plasma levels of total (4.2 vs. 4.7 mmol/l, P = 0.02) and LDL cholesterol (2.4 vs. 2.9 mmol/l, P = 0.02) in the control group, as was SNP V1119V (P = 0.04 and P = 0.03, respectively). SNPs F549F and V1119V were associated with higher systolic blood pressure (P = 0.04 and P = 0.02, respectively). There were no differences in the parameters of glucose metabolism between the genotype groups.

CONCLUSIONS

Genetic variation in LRP5 did not predispose to PA but was associated with metabolic characteristics, especially lipid profile, in healthy prepubertal children.

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.

[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 of the GAA1013→GAG polymorphism of the insulin-like growth factor-1 receptor (IGF1R) gene with premature pubarche

OBJECTIVE

A single-nucleotide polymorphism (SNP), the G variant in codon 1013 (GAA1013-->GAG) of the insulin-like growth factor-1 (IGF-1) receptor (IGFIR) gene, has been associated with higher IGF-1 concentrations in Caucasian subjects. Because elevated serum levels of IGF-1 have been described in children with premature pubarche (PP) and in adolescent girls with hyperandrogenism, we tested the a priori hypothesis that the frequency of the A-->G variant would be overrepresented among children with PP.

DESIGN

Case-control association study.

SETTING

University-based pediatric endocrinology practice.

PATIENT(S)

Sixty-nine children (63 girls and 6 boys) with PP, 52 adolescent girls with hyperandrogenism, and 92 healthy subjects.

INTERVENTION(S)

Blood was obtained for genotype analysis, glucose measurement, and hormone (A, insulin, 17-hydroxyprogesterone, and T) determinations.

MAIN OUTCOME MEASURE(S)

Frequency of the SNP in the IGF1R gene and correlation of this SNP with hormone concentrations.

RESULT(S)

Distribution of the G allele was statistically significantly different between the children with PP and the healthy control subjects, independent of insulin sensitivity.

CONCLUSION(S)

This common SNP in the IGF1R gene may be associated with PP caused by premature adrenarche in children. Because PP has been associated with higher IGF-1 concentrations, these data suggest a potential molecular basis for prior clinical observations of elevated IGF-1 concentrations in children with PP.

[Mutation screening in Angiotensin II receptors, AGTR1 and AGTR2, and evaluation of AGTR1 polymorphisms C573T and A1166C in patients with premature adrenarche]

Precocious pubarche is the appearance of pubic hair before the age of 8 years in girls and 9 years in boys. The most frequent etiology is idiopathic precocious adrenarche, suggested, after long-term follow-up, to be associated with metabolic syndrome. One of the factors involved in the genesis of precocious adrenarche is Angiotensin II (Ang II), which promotes cell proliferation and steroidogenesis through type 1 (AT1) and type 2 (AT2) receptors. In order to study Ang II receptors mutations, 50 children with idiopathic precocious adrenarche were evaluated and compared to a control group of normal individuals. Mutations were not detected in the AGTR1 and AGTR2 genes; however, two polymorphisms were identified in the AGTR1 gene: the C573T (exon 5) and the A1166C (3' untranslated region). The polymorphic allele T573 was found in 35% of the patients and 38% of controls. The polymorphic allele C1166 was present in 24% of the patients and 26% of controls. There was no statistical difference between groups. There was also no correlation between the polymorphisms and clinical and laboratory findings, as well as their family history of metabolic syndrome.

Polymorphisms in the insulin receptor substrate-1 (IRS-1) gene and the insulin receptor substrate-2 (IRS-2) gene influence glucose homeostasis and body mass index in women with polycystic ovary syndrome and non-hyperandrogenic controls

BACKGROUND

We aimed to evaluate the influence of the Gly972Arg variant of the insulin receptor substrate-1 gene (IRS-1) and the Gly1057Asp variant in IRS-2 on insulin resistance and glucose tolerance in women with polycystic ovary syndrome (PCOS) and healthy controls.

METHODS

Genotypes, allelic frequencies, indexes of insulin resistance, glucose tolerance and hormone profiles were studied in a large sample of Spanish PCOS (n = 103) women compared with a control group (n = 48) of healthy women matched for body mass index.

RESULTS

No differences in genotype or allelic frequencies were found between PCOS patients and healthy controls. When considering control subjects and PCOS patients as a whole, IRS-1 Arg972 carriers also presented with increased fasting insulin (133 +/- 60 versus 95 +/- 67 pmol/l, P = 0.008) and insulin resistance measured by homeostasis model assessment (4.3 +/- 2.1 versus 3.1 +/- 2.4, P = 0.009) compared with subjects homozygous for Gly972 alleles. These differences were even higher when restricting the analysis to PCOS patients. Subjects homozygous for the Gly1057 allele of IRS-2 presented with increased 60 and 90 min oral glucose tolerance test (OGTT) glucose levels compared with carriers of one or two Asp1057 alleles (7.9 +/- 2.1 versus 7.1 +/- 2.1 mmol/l, P = 0.042 and 7.0 +/- 2.1 versus 6.0 +/- 1.8 mmol/l, P = 0.014), and a similar tendency was observed for 120 min OGTT glucose levels.

CONCLUSIONS

The Gly972Arg in IRS-1 and Gly1057Asp in IRS-2 polymorphisms influence glucose homeostasis in premenopausal women, but are not associated with PCOS.

Genetics of polycystic ovary syndrome: searching for the way out of the labyrinth

Polycystic ovary syndrome (PCOS) is a complex and heterogeneous disorder presenting a challenge for clinical investigators. It is the most common endocrine disorder of women in reproductive age, a multifaceted reproductive, cosmetic and metabolic problem, with an enigmatic pathophysiological and molecular basis. Although the familial segregation has been noticed very early in the description of the syndrome and family studies in first-degree relatives of women diagnosed with PCOS reveal clustering of the disease, the genetic studies have not as yet determine the pattern of heredity. Part of the problem in genetic studies has been the lack of uniform criteria for diagnosis, heterogeneity of phenotypic features and the fact that the disorder is only expressed clinically in women during their reproductive years. Even within affected families and between sisters with polycystic ovaries, there is heterogeneity in presentation. However, regardless of diagnostic criteria used to identify profanes and to determine affected status in the kindred, the foundation of genetic studies suggests a strong familial component. Currently, PCOS is considered a polygenic trait that might result from the interaction of susceptible and protective genomic variants under the influence of environmental factors, whose role is under intensive investigation. Candidate genes cover a broad spectrum of an endless list of molecules which participate on every step of reproductive and metabolic pathways of this syndrome. Focused research in identification of these genes may provide valuable information and shed some light on the way out of the genomic labyrinth, elucidating the underlying pathophysiology and aiming at a more efficient therapeutic approach of this complicated endocrine disorder.

The molecular-genetic basis of functional hyperandrogenism and the polycystic ovary syndrome

The genetic mechanisms underlying functional hyperandrogenism and the polycystic ovary syndrome (PCOS) remain largely unknown. Given the large number of genetic variants found in association with these disorders, the emerging picture is that of a complex multigenic trait in which environmental influences play an important role in the expression of the hyperandrogenic phenotype. Among others, genomic variants in genes related to the regulation of androgen biosynthesis and function, insulin resistance, and the metabolic syndrome, and proinflammatory genotypes may be involved in the genetic predisposition to functional hyperandrogenism and PCOS. The elucidation of the molecular genetic basis of these disorders has been burdened by the heterogeneity in the diagnostic criteria used to define PCOS, the limited sample size of the studies conducted to date, and the lack of precision in the identification of ethnic and environmental factors that trigger the development of hyperandrogenic disorders. Progress in this area requires adequately sized multicenter collaborative studies after standardization of the diagnostic criteria used to classify hyperandrogenic patients, in whom modifying environmental factors such as ethnicity, diet, and lifestyle are identified with precision. In addition to classic molecular genetic techniques such as linkage analysis in the form of a whole-genome scan and large case-control studies, promising genomic and proteomic approaches will be paramount to our understanding of the pathogenesis of functional hyperandrogenism and PCOS, allowing a more precise prevention, diagnosis, and treatment of these prevalent disorders.

Prevalence of CYP21 mutations and IRS1 variant among women with polycystic ovary syndrome and adrenal androgen excess

OBJECTIVE

To determine whether frequencies of the mutations in the 21-hydroxylase (CYP21) gene and the G972R variant of the insulin receptor substrate-1 (IRS1) gene are increased in women with polycystic ovary syndrome (PCOS) and adrenal androgen (AA) excess.

DESIGN

Prospective case-control study.

SETTING

University reproductive endocrinology laboratory and outpatient clinic.

PATIENT(S)

Consecutive patients of non-Hispanic white race diagnosed with PCOS (n = 114) and healthy controls (n = 95).

INTERVENTION(S)

Blood and DNA sampling before hormonal therapy.

MAIN OUTCOME MEASURE(S)

Polycystic ovary syndrome patient and healthy control genotypes, with the CYP21 and IRS1 variants.

RESULT(S)

Fifty-four PCOS patients with (DHEAS >3000 ng/mL) and 55 without (DHEAS <2500 ng/mL) AA excess, respectively, were studied. Of 109 patients studied, 16 (14.7%) were found to be heterozygous carriers of mutations in the CYP21 gene. Of these 16, 10 (62.5%) had excessive AA secretion (i.e., excess DHEAS levels). Fifteen patients (13.8%) were found to be heterozygous carriers of the IRS1 variant; 9 (60.0%) of these 15 had excessive AA secretion. There were no significant differences in the allele frequency of CYP21 mutations or the IRS1 variant between PCOS patients with and without AA excess, and controls. None of the subjects were found to be homozygous carriers of CYP21 mutations or the IRS1 variant. Combined heterozygosity for CYP21 mutations and the IRS1 variant was limited to women with PCOS and excessive AA (n = 3).

CONCLUSION(S)

The G972R variant of the IRS1 gene might represent a modifier locus among women who are heterozygous carriers of CYP21 mutations, potentially increasing their risk of developing AA excess in PCOS. Nonetheless, this IRS1 variant and CYP21 mutations seem to play a limited role in the development of PCOS in the population studied.

The genetics of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a heterogeneous disorder. There is evidence for a genetic component in PCOS based on familial clustering of cases. The majority of the evidence supports an autosomal dominant form of inheritance. Steroidogenesis has been shown to be upregulated in PCOS theca cells, suggesting that the genetic abnormality in PCOS affects signal transduction pathways controlling the expression of a family of genes. Although a number of candidate genes have been proposed, the putative PCOS gene(s) has yet to be identified. Linkage and association studies implicate a region near the insulin receptor gene at chr 19p13.3. New genetic approaches, such as microarray technology, hold promise for elucidation of the pathophysiology underlying PCOS.

Genetic Basis of Metabolic Abnormalities in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a common heterogeneous disorder characterized by hyperandrogenism and chronic anovulation. The syndrome is frequently associated with an increased risk for insulin resistance and type 2 diabetes mellitus; obesity exacerbates insulin resistance and favors the progression from impaired glucose tolerance to diabetes in these patients. In young women, precocious pubarche and hyperinsulinemia are early manifestations of PCOS. The familial clustering of women with PCOS suggests that heredity is implicated in the origin of the syndrome. However, genetic approaches to its pathogenesis have been hampered by the heterogeneity of phenotypic features within families, and the lack of uniform criteria for diagnosis. Currently, PCOS is considered a polygenic trait that might result from the interaction of susceptibility and protective genomic variants under the influence of environmental factors. Both linkage analysis and association studies are valid tools for the study of the genetics of PCOS. Candidate genes for PCOS include those related to androgenic pathways and metabolic associations of the syndrome. More recently, genes encoding inflammatory cytokines have been identified as target genes for PCOS, as proinflammatory genotypes and phenotypes are also associated with obesity, insulin resistance, type 2 diabetes, PCOS, and increased cardiovascular risk. This paper reviews the candidate genes involved in the metabolic pathways that are altered in patients with PCOS. Despite a significant amount of research in this area, none of the genes studied so far has been identified as the PCOS susceptibility gene for the majority of cases. PCOS is the first component of the metabolic syndrome to be detected in many women, so the identification and correct diagnosis of PCOS has important preventive and therapeutic implications for the affected women and their families. In the future, new therapeutic approaches to PCOS will rely on knowing the genes, environmental influences, and etiologic mechanisms associated with the disorder.