Insulin resistance and polycystic ovarian syndrome.

Insulin resistance (IR) and polycystic ovarian syndrome (PCOS) appear as linked phenomena, although this is not easy to obviate in common forms of PCOS while it is evident in the rare cases of extreme IR and hyperinsulinism (HI). Experimental data indicate that insulin could interfere with the local insulin-like growth factor systems in ovaries, and presumably in adrenals and in the hypothalamic pituitary system. The female puberty system offers a physiological model to explain the gonadotropic action of insulin. In patients with IR, HI could induce a state of hyperpuberty, leading to the constitution of PCOS during adolescence.     

Molecular mechanisms of insulin resistance in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrinopathy of unknown aetiology that affects women of reproductive age. During the past ten years, defective insulin activity in PCOS has been demonstrated in target tissues and causes insulin resistance and hyperinsulinaemia. Furthermore, presence of insulin receptors in the ovarian tissue and overproduction of androgens by theca cells leads to characteristic hyperandrogenaemia. Recent data suggest a divergence in post-receptor signalling pathways for insulin in its target tissues (muscle, adipocytes and ovarian tissue), where the metabolic pathway of insulin activity is defective, whereas the activation of steroidogenesis is maintained. Investigators are still searching for clues to understand the cause of this enigmatic syndrome, despite great advances in molecular medicine and genetics.     

Metabolic syndrome in polycystic ovary syndrome

Both metabolic syndrome (MS) and polycystic ovary syndrome (PCOS) are common among women. The exact prevalence of MS in women with PCOS is dependent upon the diagnostic criteria used for each. However, the frequent co-occurrence of both MS and PCOS in women is suggestive of a common aetiology. In this short review article we argue that insulin resistance, as a consequence of abdominal obesity, may represent such a common aetiology. We also review the literature on the prevalence of MS in women with PCOS and consider the impact that the particular criteria used to diagnose both MS and PCOS may have had on these estimates of prevalence.     

Elevated ghrelin plasma levels in patients with polycystic ovary syndrome.

Polycystic ovary syndrome is a common endocrine disorder in women. It is associated with hirsuitism, obesity, insulin resistance, abnormality in the growth hormone/insulin-like growth factor I (IGF-1) axis and polycystic ovaries. The etiology of PCOS has not been clarified. Ghrelin is an endogenous ligand of the growth hormone secretagogue receptor. It is mainly secreted by stomach cells but has also been shown to be present in hypothalamus, pituitary, pancreas and gonads. Ghrelin is a regulator of energy homeostasis and GH secretion. The influence of ghrelin on insulin secretion and gonadal function is known. Since ghrelin may play an important role in pathophysiology of PCOS, we studied ghrelin levels in a group of 52 women with PCOS and in 16 women in a control group. Plasma levels of insulin, total testosterone, SHBG, LH, and FSH were also measured. In conclusion, PCOS women have higher ghrelin levels than controls. Ghrelin negatively correlates with BMI and insulin levels in PCOS group. A relation between ghrelin and SHBG was observed. Our data suggest that ghrelin could be the possible link in PCOS etiology.     

Hyperinsulinism and insulin resistance in the polycystic ovary syndrome as tested with tolbutamide

The aim of this research was to study both insulin secretion and insulin resistance index (IRI) in seventeen females, aged 16-30, affected by polycystic ovarian syndrome. The diagnosis was made using clinical, hormonal, radiological and echographic criteria. Eight healthy women, carefully matched with our patients for age and for statistical obesity incidence, were studied as controls. Both glycemic and insulinemic curves, areas, insulinemic/glycemic area ratio (IRI) were studied by tolbutamide test (1 g i.v.). Areas were assessed by planimeter, blood glucose by Trinder method, blood insulin by a RIA method, statistical study by t Student test and correlation coefficients. These latter were determined by comparing individual plasma testosterone, FSH, LH and LH/FSH ratio values together with urinary total 17-ketosteroid and delta HEA output values on the one hand and insulin areas and IRI values on the other. Increased glycemic areas, insulinemic peaks and areas, associated with markedly increased IRI values, were observed in the patients. A correlation exists between hyperinsulinism, insulin resistance on the one hand and increased urinary androgens output on the other. delta HEA resulted particularly increased over other androgenic fractions.     

Neuroendocrine dysfunction in polycystic ovary syndrome

Polycystic ovarian syndrome (PCOS) is a common disorder characterized by ovulatory dysfunction and hyperandrogenemia (HA). Neuroendocrine abnormalities including increased gonadotropin-releasing hormone (GnRH) pulse frequency, increased luteinizing hormone (LH) pulsatility, and relatively decreased follicle stimulating hormone contribute to its pathogenesis. HA reduces inhibition of GnRH pulse frequency by progesterone, causing rapid LH pulse secretion and increasing ovarian androgen production. The origins of persistently rapid GnRH secretion are unknown but appear to evolve during puberty. Obese girls are at risk for HA and develop increased LH pulse frequency with elevated mean LH by late puberty. However, even early pubertal girls with HA have increased LH pulsatility and enhanced daytime LH pulse secretion, indicating the abnormalities may begin early in puberty. Decreasing sensitivity to progesterone may regulate normal maturation of LH secretion, potentially related to normally increasing levels of testosterone during puberty. This change in sensitivity may become exaggerated in girls with HA. Many girls with HA-especially those with hyperinsulinemia-do not exhibit normal LH pulse sensitivity to progesterone inhibition. Thus, HA may adversely affect LH pulse regulation during pubertal maturation leading to persistent HA and the development of PCOS.     

Proteomics and polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a complex endocrine disorder of heterogeneous etiology. Proteomics techniques have been used for elucidating the physiopathology of PCOS, yet the proteins identified so far were rarely the same across tissues and studies. The present review discusses the current challenges in the application of proteomics to the study of PCOS. A well-defined research design and an appropriate selection of study populations, samples and proteomic platforms are essential in clinical proteomics. Furthermore, the findings derived from proteomic approaches should be validated by complementary techniques, and the reproducibility of the results has ideally to be confirmed by different studies. Only when meeting these requirements, the proteins identified by proteomic techniques should be considered as candidates for future studies aiming to define specific molecular phenotypes of PCOS and their possible role in the metabolic and hormonal abnormalities characteristic of this syndrome.     

Lipid disturbances in women with polycystic ovary syndrome.

Small but detectable disturbances concerning blood lipid levels manifested by somewhat higher concentrations of LDL-cholesterol and triglycerides as well as higher values of atherogenic indices expressing the ratio of cholesterol present in atherogenic lipoprotein fractions to that present in atheroprotective HDL fraction have been shown to exist in 36 women with polycystic ovary syndrome. HDL-cholesterol concentration was lower in women with polycystic ovary syndrome than in healthy women. The disturbances described above were more pronounced in obese patients. No correlation was found between the disturbances in lipid levels and hormonal disturbances particularly hyperandrogenemia.     

Evaluation of insulin resistance and plasma levels for visfatin and resistin in obese and non-obese patients with polycystic ovary syndrome

This study was designed to evaluate insulin resistance and plasma levels of visfatin and resistin in obese and non-obese patients with polycystic ovary syndrome (PCOS).A total of 37 premenopausal PCOS patients with (n = 18, mean (SD) age: 27.5 (5.7 years) or without obesity (n = 19, mean (SD) age: 23.7 (3.1) years) and healthy volunteers (n = 18, mean (SD) age:29.8 (4.1) years) were included in this study. Data on clinical characteristics, glycemic parameters and lipid parameters were recorded for each subject as were plasma visfatin and resistin levels. Mean (SD) HOMA-IR values were significantly higher in obese PCOS patients (3.4 (1.7)) compared with non-obese PCOS patients (2.0 (1.2), p<0.01) and controls (1.6 (0.8), p<0.01). No significant difference was noted between study groups in terms of plasma resistin (ng/mL) or visfatin (ng/mL) levels. There was no correlation between serum plasma visfatin (r = 0.127, p = 0.407) and resistin (r = -0.096, p = 0.544) levels and HOMA-IR. In conclusion, our findings revealed increased likelihood of metabolic and dyslipidemic manifestations in obese compared to non-obese PCOS patients, while no significant difference was noted in visfatin and resistin levels among PCOS patients in terms of co-morbid obesity and in comparison to controls.     

Genetic aspects of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common heterogenous endocrine disorder associated with amenorrhoea (or oligomenorrhoea), hyperandrogenism, hirsutism, obesity, insulin resistance, and an approximately 7-fold increased risk of type 2 diabetes mellitus (NIDDM - non-insulin dependent diabetes mellitus). It is a leading cause of female infertility. The prevalence of PCOS among reproductive-age women has been estimated at 4%-12%. Familial aggregation of this syndrome is well established. There are also ethnic and racial variations in the prevalence of the syndrome and its symptoms. Multiple biochemical pathways have been implicated in the pathogenesis of PCOS. Several genes from these pathways have been tested include genes involved in steroid hormone biosynthesis and metabolism (StAR, CYP11, CYP17, CYP19 HSD17B1-3, HSD3B1-2), gonadotropin and gonadal hormones action (ACTR1, ACTR2A-B, FS, INHA, INHBA-B, INHC, SHBG, LHCGR, FSHR, MADH4, AR), obesity and energy regulation (MC4R, OB, OBR, POMC, UCP2-3), insulin secretion and action (IGF1, IGF1R, IGFBPI1-3, INS VNTR, IR, INSL, IRS1-2, PPARG) and many others. Most women with PCOS, both obese and lean, have a degree of insulin resistance. The minisatellite of insulin gene (INS VNTR), especially class III alleles and III/III genotypes might not only determine the predisposition to anovulatory PCOS but also the concomitant risk for development of type 2 diabetes. The function of the insulin receptor (IR) is probably normal in woman with PCOS. However abnormal serine phosphorylation in the receptor may impair signal transduction accounting for a post-binding defect in insulin action. Serine phosphorylation is also involved in the postranslational regulation of 17,20-lyase activity (CYP17). There may be a common aetiology for both insulin resistance and hyperandrogenism. Polymorphic alleles of both IRS-1 and IRS-2 (insulin receptor substrate 1 - 2), alone or in combination, may have a functional impact on the insulin-resistant component of PCOS. There is no evidence to suggest that follistatin gene polymorphisms play a role in the pathogenesis of insulin resistance in PCOS women. PCOS appears to be associated with the absence of the four-repeat-units allele in a polymorphic region of pentanucleotide (TTTTA)n repeats within CYP11A gene, which encodes cytochrome P450scc. It has been hypothesized that up-regulation of this enzyme could lead to increased androgen production. There is no evidence of any association of alleles of CYP19 gene (encoding cytochrome P450arom) with PCOS. Association exists between androgen receptor gene (AR) polymorphisms an androgens action in PCOS. Increased hirustism and decreased CAG repeat length within AR gene has been also demonstrated in women with normal testosterone levels. Expression of estrogen receptor (ERs) as well as 5-alpha-reeducates (SRD5A1-2 genes) activity was analysed in granulosa (GC) and theca cells (TC). The results of this study demonstrate that there are significant alterations in the expression of ERalpha and ERbeta in PCOS that may be related to abnormal follicular development. On the other hand elevated SRD5A activity in polycystic ovaries supported the hypothesis that 5-alpha-reduced androgens may play a role in the pathogenesis of the syndrome. The genetic aetiology of PCOS remains unknown. There are a number of interlinking factors that affects expression of PCOS. Single cause of PCOS is unlikely. Other possible mechanisms in pathogenesis of PCOS are discussed.     

Lipid and lipoprotein profile in women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine disorder characterized by obesity-related risk factors for cardiovascular disease. The objective of our study was to determine values of key lipid and lipoprotein fractions in PCOS, and their possible relation to insulin resistance. A total of 75 women with PCOS (aged 23.1 +/- 5.1 years, BMI 24.9 +/- 4.7 kg/m(2)), and 56 age- and BMI-matched controls were investigated. In all subjects, basal glucose, cholesterol (total, HDL, and LDL), oxidized LDL (OxLDL), triglycerides, apolipoprotein (apo)A1, apoB, and apoE, nonesterified fatty acids, insulin, testosterone, sex hormone-binding globulin, homeostasis model assessment (HOMA) index, and free androgen index were determined in the follicular phase of the cycle. PCOS patients compared with controls had increased indices of insulin resistance, basal insulin (p < 0.001), and HOMA index (p < 0.001), and worsened insulin resistance-related dyslipidemia with decreased HDL cholesterol (p < 0.01), elevated triglycerides (p = 0.010), and pronounced LDL oxidation (p < 0.001). In conclusion, characteristic dyslipidemia of insulin resistance and unfavorable proatherogenic lipoprotein ratios were present only in women with PCOS and not in controls. Elevated OxLDL and the relation of apoE and nonesterified fatty acids with insulin resistance suggest that women with PCOS are at increased risk for premature atherosclerosis.     

The management of infertility associated with polycystic ovary syndrome

Polycystic ovary syndrome [PCOS] is the commonest cause of anovulatory infertility. Treatment modes available are numerous mainly relying on ovarian stimulation with FSH, a reduction in insulin concentrations and a decrease in LH levels as the basis of the therapeutic principles. Clomiphene citrate is still the first line treatment and if unsuccessful is usually followed by direct FSH stimulation. This should be given in a low dose protocol, essential to avoid the otherwise prevalent complications of ovarian hyperstimulation syndrome and multiple pregnancies. The addition of a GnRH agonists, while very useful during IVF/ET, adds little to ovulation induction success whereas the position of GnRH antagonists is not yet clear. Hyperinsulinemia is the commonest contributor to the state of anovulation and its reduction, by weight loss or insulin sensitizing agents such as metformin, will alone often restore ovulation or will improve results when used in combination with other agents. Laparoscopic ovarian drilling is proving equally as successful as FSH for the induction of ovulation, particularly in thin patients with high LH concentrations. Aromatase inhibitors are presently being examined and may replace clomiphene in the future. When all else has failed, IVF/ET produces excellent results. In conclusion, there are very few women suffering from anovulatory infertility associated with PCOS who cannot be successfully treated today.     

Dyslipidemia in relation to body mass index and insulin resistance in Chinese women with polycystic ovary syndrome

Dyslipidemia is a common metabolic disorder in women with polycystic ovary syndrome (PCOS) and has been reported to be different in PCOS sufferers from various ethnic and geographic backgrounds. This study aims to investigate the prevalence of dyslipidemia in Chinese women with PCOS and its relationship to body mass index (BMI) and insulin resistance (IR). In this paper, a retrospective study was performed on 507 PCOS patients and 1246 age- and BMI-matched controls. Anthropometric indices of hormonal, adiposity, and metabolic variables were measured. All patients were divided into subgroups according to BMI and the homeostasis model assessment (HOMA) values. Accordingly, the prevalence of IR was 38.1 percent in our subjects. We found that mean fasting total triglyceride, low density lipoprotein (LDL) cholesterol and total cholesterol levels were significantly higher and the mean high density lipoprotein (HDL) cholesterol level was significantly lower in the IR group than in the non-IR (NIR) group. The prevalence of dyslipidemia was 24.7 percent in PCOS patients and the prevalence of dyslipidemia was significantly higher in the IR group than in the NIR group (39.9 percent vs 15.3 percent, P<0.05). The HOMA index was found to be positively correlated with TG, TC and LDL, and negatively correlated with HDL. TG and HDL levels remained significantly correlated with HOMA even after adjustment for BMI. Generally, the prevalence of various patterns of dyslipidemia in PCOS patients increased with HOMA value. In conclusion, the prevalence of IR and dyslipidemia were both found to be high in PCOS women in our study, although no higher than other ethnicities. Lipid abnormality was demonstrated to be associated with IR and BMI in Chinese PCOS women. We speculate that insulin sensitizer might ameliorate dyslipidemia through improving IR in PCOS women.