A dopamine D3 receptor genotype is associated with hyperandrogenic chronic anovulation and resistant to ovulation induction with clomiphene citrate in female Hispanics

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.

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.

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.

Growth hormone insufficiency and its impact on ovarian function

Growth hormone (GH) and the insulin-like growth factor-I (IGF-I) play significant roles in pubertal development, menarche, the menstrual cycle, fertility, and reproduction. Growth hormone deficiency or insufficiency causes a delay in the onset of puberty and in its normal course unless treated with synthetic GH. It seems that GH affects the ovary during puberty both indirectly through the gonadotropins and IGF-I, and directly through its effect on steroidogenesis. The GH axis is activated by small increases in circulating estrogens, which initiate large increases in GH during puberty. The reproductive function of the female is also affected by GH. GH acts on the ovary affecting gametogenesis and steroidogenesis. GH receptor mRNA and protein have been found in ovarian cells, and this suggests that the direct action of GH provides an important modulatory effect on gonadotropin-dependent and -independent functions. It also affects the maturation of the follicle and gamete, and thereby plays a facilitatory role in fertility. The majority of women with GH-deficiency, but not all, require assisted reproductive technologies to induce ovulation. Many women with polycystic ovary syndrome (PCOS) have an impaired GH response to stimulation with Levo-Dopa and GH releasing hormone (GHRH). Hyperandrogenism in PCOS may contribute to the reduced GH secretion because testosterone directly stimulates somatostatin release. Reduction of the excessive androgens facilitates the dopaminergic control of GH. In conclusion, GH-insufficient states disrupt ovarian function, causing problems in sexual maturation, the menstrual cycle, and the reproductive ability of the female.

Le syndrome des ovaires polykystiques en période péri-pubertaire : polymorphisme clinique, biologique, métabolique et génétique

Polycystic ovary syndrome (PCOS) is a common cause of hyperandrogenism in adolescent girls. In its complete post menarchal expression, the syndrome is characterized by the association of typical clinical, biological, and ultrasonographic findings. Many factors have contributed to our knowledge of different clinical forms of PCOS in adolescent girls. They are helpful for clarifying misleading situations in a period of life when diagnosis of PCOS implies a treatment for many years and may interfere with gynecological outcome. During the last 3 years, we had the opportunity to manage in our unit 45 adolescent girls with ovarian hyperandrogenism: 32 of them had PCOS and the other 13 functional ovarian hyperandrogenism defined by clinical and biological hyperandrogenism without ultrasonographic abnormality. In this review, we report, from our personal experience as well as from recent literature data, the different clinical expressions of PCOS in the pubertal period: the classical post menarchal form, the exceptional pre menarchal form, the post precocious pubarche and the post precocious puberty forms, the familial expression as well as the dominant metabolic expression.

Molecular progress in infertility: polycystic ovary syndrome

OBJECTIVE

To review the evidence that polycystic ovary syndrome is a genetic disease.

DESIGN

Review of published literature.

RESULTS

The existing literature provides a strong basis for arguing that PCOS clusters in families. However, the mode of inheritance of the disorder is still uncertain, although the majority of studies are consistent with an autosomal dominant pattern, modified perhaps by environmental factors. In addition, studies on PCOS cells (theca, muscle, and adipocytes) in culture have documented a persistent biochemical and molecular phenotype that distinguishes them from normal cells. Although several loci have been proposed as PCOS genes including CYP11A, the insulin gene, and a region near the insulin receptor, the evidence supporting linkage is not overwhelming. The strongest case can be made for the region near the insulin receptor gene, as it has been identified in two separate studies. However, the responsible gene at chromosome 19p13.3 remains to be identified. Association studies have provided a number of potential loci with genetic variants that may create or add to a PCOS phenotype, including Calpain 10, IRS-1 and -2, and SHBG.

CONCLUSIONS

Collectively, these findings are consistent with the concept that a gene or several genes are linked to PCOS susceptibility. Because the mutations/genotypes associated with PCOS are rare, and their full impact on the phenotype incompletely understood, routine screening of women with PCOS or stigmata of PCOS for these genetic variants is not indicated at this time. Currently the treatment implications for individually identified genetic variants is uncertain and must be addressed on a case by case basis.

Polycystic ovary syndrome: a single gene mutation or an evolving set of symptoms

Polycystic ovary syndrome is one of the most common endocrinopathies among women. Nevertheless, there is no one single acceptable definition for this syndrome, its pathophysiology is not completely understood and its etiology remains an enigma. Several studies have examined the genetic basis of polycystic ovary syndrome with varying results, probably caused by the different criteria used to define the syndrome. These studies, together with studies that deal with reclassification of polycystic ovary syndrome, are described in the following review. Furthermore, a simplified alternative approach to this symptom complex is proposed.

Androgen excess contributes to altered growth hormone/insulin-like growth factor-1 axis in nonobese women with polycystic ovary syndrome

OBJECTIVE

To investigate the relationship between ovarian androgen excess and impaired growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis in nonobese women with polycystic ovary syndrome (PCOS).

DESIGN

A prospective, controlled clinical study.

SETTING

Reproductive Endocrine Unit, Department of Obstetrics and Gynecology, Jinling Hospital, Nanjing University School of Clinical Medicine.

PATIENT(S)

Six patients with PCOS with both clomiphene resistance and gonadotropin hyperreponsiveness and six controls with regular cycles, matched for age and body mass index (BMI).

INTERVENTION(S)

Bilateral ovarian wedge resection (OWR) was performed to induce ovulation surgically for these refractory women with PCOS. A GH stimulation test with oral L-dopa was arranged for controls and for patients with PCOS before and again 6 months later after OWR.

MAIN OUTCOME MEASURE(S)

Plasma GH, IGF-1, FSH, LH, testosterone, androstenedione, estradiol, progesterone, prolactin, insulin, and glucose.

RESULT(S)

Basal levels and areas under the response curve of GH and GH-IGF-1 ratio to L-dopa were significantly lower in patients with PCOS before surgery than those of controls. The OWR in patients with PCOS obviously reduced their androstenedione and testosterone levels and insulin-glucose ratios, and increased the GH and GH-IGF-1 responses to L-dopa.

CONCLUSION(S)

Impaired somatotrophic axis caused by a defect in central dopaminergic activity may be responsible for severe anovulation in these women with PCOS, which could be reversed by removing excessive androgens with OWR.

Polycystic ovary syndrome. Phenotype to genotype

Available studies suggest there is a strong familial component to PCOS regardless of the diagnostic criteria used to ascertain probands and to assign affected status in kindreds. Investigation of all kindred members using the same systematic screen for metabolic and reproductive abnormalities strengthens the validity of conclusions. There is no substitute for direct biometric or biochemical proof of the phenotype. Initial studies by the author and his colleagues suggest that hyperandrogenemia in sisters is a valid phenotype characteristic. Further study is necessary to establish other phenotypes in the families. Large family clusterings of PCOS offer the best opportunity for identifying unique strains of PCOS. These families may represent a homogeneous etiology of the syndrome despite significant phenotypic heterogeneity within a given pedigree. Linkage analysis should be performed between polymorphic markers spaced at regular genetic intervals, and these familial traits may identify critical regions for further investigation.

Dopamine D3 receptor polymorphism is not associated with the polycystic ovary syndrome

OBJECTIVE

To determine if a polymorphism of the dopamine D3 receptor gene (2 allele), which has been reported previously to be associated with polycystic ovary syndrome (PCOS) in a population of United States Hispanic women, is associated with the disorder in the southeastern United States.

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 = 152) and healthy controls (n = 96).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Patient and control dopamine D3 receptor genotypes, with the 1 allele representing the wild type and the 2 allele denoting a highly prevalent polymorphism.

RESULT(S)

No difference was noted in the distribution of the three dopamine D3 receptor genotypes (i.e., 1:1, 1:2, and 2:2) among PCOS patients as compared with controls. Furthermore, in contrast to a previous report, the 2:2 genotype was not more prevalent among PCOS patients than among controls.

CONCLUSION(S)

Our population of non-Hispanic white women from the southeastern United States did not demonstrate an association between a dopamine D3 receptor polymorphism and PCOS.

Premature pubarche, ovarian hyperandrogenism, hyperinsulinism and the polycystic ovary syndrome: from a complex constellation to a simple sequence of prenatal onset

Adolescent girls with a history of premature pubarche have an increased incidence of functional ovarian hyperandrogenism [a form of polycystic ovary syndrome (PCOS)] at adolescence, which is usually associated with hyperinsulinemia and dyslipemia. The hyperinsulinemia and lipid disturbances can often be detected in the prepubertal period and throughout puberty, and are associated with an exaggerated ovarian androgen synthesis. Birthweight SD scores are lower in premature pubarche girls than in control girls, and particularly so in those girls who show hyperinsulinemia and subsequently develop ovarian hyperandrogenism. Therefore, although the mechanisms interlinking the triad of premature pubarche, hyperinsulinism and ovarian hyperandrogenism remain enigmatic, these data indicate that the triad may result, at least in part, from a common early origin, rather than from a direct interrelationship later in life.

Insulin resistance and the polycystic ovary syndrome: mechanism and implications for pathogenesis

It is now clear that PCOS is often associated with profound insulin resistance as well as with defects in insulin secretion. These abnormalities, together with obesity, explain the substantially increased prevalence of glucose intolerance in PCOS. Moreover, since PCOS is an extremely common disorder, PCOS-related insulin resistance is an important cause of NIDDM in women (Table 3). The insulin resistance in at least 50% of PCOS women appears to be related to excessive serine phosphorylation of the insulin receptor. A factor extrinsic to the insulin receptor, presumably a serine/threonine kinase, causes this abnormality and is an example of an important new mechanism for human insulin resistance related to factors controlling insulin receptor signaling. Serine phosphorylation appears to modulate the activity of the key regulatory enzyme of androgen biosynthesis, P450c17. It is thus possible that a single defect produces both the insulin resistance and the hyperandrogenism in some PCOS women (Fig. 19). Recent studies strongly suggest that insulin is acting through its own receptor (rather than the IGF-I receptor) in PCOS to augment not only ovarian and adrenal steroidogenesis but also pituitary LH release. Indeed, the defect in insulin action appears to be selective, affecting glucose metabolism but not cell growth. Since PCOS usually has a menarchal age of onset, this makes it a particularly appropriate disorder in which to examine the ontogeny of defects in carbohydrate metabolism and for ascertaining large three-generation kindreds for positional cloning studies to identify NIDDM genes. Although the presence of lipid abnormalities, dysfibrinolysis, and insulin resistance would be predicted to place PCOS women at high risk for cardiovascular disease, appropriate prospective studies are necessary to directly assess this.

Current concepts of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) may be loosely defined as unexplained hyperandrogenism, with variable degrees of cutaneous symptoms, anovulatory symptoms, and obesity. The vast majority of patients with the full-blown Stein-Leventhal syndrome have functional ovarian hyperandrogenism (FOH). However, FOH often occurs without the LH excess or polycystic ovaries of classic PCOS. Functional adrenal hyperandrogenism (FAH) is often found in the syndrome, but it is less closely associated with anovulatory symptoms than is FOH. The vast majority of FOH seems to arise from abnormal regulation (dysregulation) of ovarian androgen secretion. This typically is due to escape from desensitization to luteinizing hormone (LH); this appears to occur because of a breakdown in the processes that normally coordinate ovarian androgen and oestrogen secretion so as to prevent hyperoestrogenism. Similar dysregulation of adrenal androgen secretion in response to ACTH seems to account for most FAH. Dysregulation of androgen secretion may affect the ovary alone (isolated FOH), the adrenal alone (isolated FAH), or both together. Modest insulin resistance is common in PCOS/FOH, and the resultant hyperinsulinaemia is a major candidate as the cause of the dysregulation. The hyperinsulinaemia may arise from either 'nature' (genetic defects) or 'nurture' (exogenous obesity). Although hyperinsulinaemia alone does not have an obvious effect on steroidogenesis, it may act in genetically predisposed women as a 'second hit' to unmask latent abnormalities in steroidogenesis. The ovary, the adrenal cortex, and several other organs paradoxically function as if responding to the hyperinsulinaemic state in spite of resistance to the effects of insulin on glucose metabolism. PCOS should be viewed as an early manifestation of a hyperinsulinaemic condition that will predispose to cardiovascular and metabolic complications later in life. A subset of PCOS patients appear to have not only insulin resistance but also beta-cell secretory dysfunction, which may indicate a relationship of the disorder to NIDDM. The fundamental genetic defects remain to be elucidated.