***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: CONTEXT Vascular endothelial growth factor A ( VEGF-A ) is a potent cytokine that promotes angiogenesis and vascular permeability . After controlled ovarian stimulation ( COS ) for in vitro fertilization ( IVF ) , excessive VEGF-A production can occur , particularly in women with polycystic ovarian syndrome ( PCOS ) ; however , it is unclear whether the regulation of VEGF-A production is different between PCOS and non-PCOS women . OBJECTIVE The aim of this study was to determine whether there were differences in the dose- and time-dependent effects of insulin and IGFs on VEGF-A production by luteinized granulosa cells ( LGCs ) from women with and without PCOS . DESIGN AND SETTING A prospect i ve comparative experimental study was conducted at an institutional practice . PATIENTS Patients included six PCOS and six non-PCOS women undergoing COS and IVF .  INTERVENTIONS Interventions included COS for IVF . MAIN OUTCOME MEASURES VEGF-A levels in culture media were collected daily for 3 d from LGCs after incubation with variable doses of insulin , IGF-I , and IGF-II in the presence and absence of LH . RESULTS In both study groups , exposure to LH alone did not alter VEGF-A levels . However , insulin or IGF increased VEGF-A levels within 1 d and appeared to synergize with LH at 3 d. VEGF-A production by non-PCOS LGCs was more sensitive to IGF exposure , whereas PCOS cells were more sensitive to insulin . Although an increase in DNA content ( P < 0.05 ) was noted in cultures of PCOS cells , progesterone levels were lower compared with non-PCOS LGCs . CONCLUSION Insulin and IGFs promote VEGF-A production in LGCs , but the response patterns are different when cells from PCOS and non-PCOS women are compared BACKGROUND The aim of this study was to determine whether , in polycystic ovarian syndrome ( PCOS ) patients , HCG action prolonged for 4 h improves the action of angiogenic substances [ ovarian renin angiotensin system and vascular endothelial growth factor ( VEGF ) ] , and consequently follicular maturation , oocyte quality and oocyte fertilization competence . METHODS In this prospect i ve study 20 patients with PCOS undergoing IVF were included .  Oocyte retrieval was carried out either 34 or 38 h after HCG administration . Each follicle was analysed for prorenin , active renin , VEGF and estradiol . Oocytes were evaluated for quality ( mature , immature , degenerated oocytes ) , as were the embryos ( low or high ) . RESULTS In the HCG + 38 h group there were 245 follicles , and in the HCG + 34 h group 240 follicles . In the HCG + 38 h group , log active renin was lower ( 2.78 + /- 0.20 versus 2.91 + /- 0.25 ; P < 0.001 ) and VEGF higher ( 2276.0 + /- 790.1 versus 1946.6 + /- 954.5 pg/ml ; P < 0.001 ) . The odds ratio for obtaining oocytes from follicles was 1.6 [ 95 % confidence interval ( CI ) 1.1 - 2.6 ; P = 0.02 ] , and for developing high quality embryos 7.6 ( 95 % CI 2.8 - 20.9 ; P < 0.001 ) in favour of the HCG + 38 h group . CONCLUSIONS Follicular maturation and oocyte quality are related to the intrafollicular influences of active renin and VEGF in a time-dependent manner after HCG administration , whereas fertilization competence is related to VEGF only OBJECTIVE To determine the concentration of angiogenic factors ( vascular endothelial growth factor [ VEGF ] , basic fibroblast growth factor [ bFGF ] , and angiogenin ) in the follicular fluid ( FF ) and oocyte-cumulus complex culture medium ( CM ) of women undergoing IVF  and to investigate the association of the concentrations with the maturity and fertilization of the oocyte . DESIGN Prospect i ve study . SETTING Academic tertiary-care institution . PATIENT(S ) IVF patients with unexplained or tubal factor infertility . INTERVENTION(S ) Analysis of VEGF , bFGF , and angiogenin FF and CM concentrations . MAIN OUTCOME MEASURE(S ) Oocyte maturity and fertilization and FF and CM angiogenic factor concentrations . RESULT ( S ) VEGF , bFGF , and angiogenin were determined in FF and CM . FF angiogenin concentrations were significantly higher when the oocyte was mature versus immature . CM VEGF concentrations were significantly higher when the oocyte was nonfertilized versus fertilized . Positive correlations were observed between angiogenic factors in CM . CONCLUSION ( S ) VEGF , bFGF , and angiogenin ( determined for the first time ) are secreted in the FF and CM . Elevated CM VEGF concentrations , probably implying oocyte-cumulus complex hypoxia , are negatively associated with oocyte fertilization . Elevated FF angiogenin concentrations are positively associated with oocyte maturity , possibly indicating angiogenin 's biological role beyond neovascularization To test the hypothesis that increased serum levels of vascular endothelial growth factor ( VEGF ) in women with polycystic ovaries or the polycystic ovary syndrome ( PCOS ) result from excess release by ovarian granulosa cells . Prospect i ve study . Academic research setting . Twenty women undergoing IVF treatment , of whom 10 had normal ovaries and 10 had polycystic ovaries .  Human granulosa lutein cells were isolated from follicular fluid obtained on the day of oocyte retrieval . Release of VEGF was assessed after co-incubation of granulosa lutein cells with gonadotropins and insulin .  Serum and follicular fluid concentrations of VEGF were measured . Release of VEGF from granulosa lutein cells and serum levels of VEGF . Incubation with human hCG , and luteinizing hormone increased release of VEGF into the culture medium . Insulin alone did not increase release of VEGF , but addition of insulin increased hCG-stimulated release of VEGF . Serum and follicular fluid VEGF concentrations and the amount VEGF released from granulosa lutein cells obtained from women with polycystic ovaries or PCOS and those who developed the ovarian hyperstimulation syndrome were greater than those from granulosa lutein cells obtained from women with normal ovaries and those who did not develop the ovarian hyperstimulation syndrome . The amount of VEGF released by granulosa lutein cells is gonadotropin dependent and is augmented by insulin . The increased circulating concentrations of VEGF in women with PCOS may not only be due to an increased number of actively secreting granulosa lutein cells but also due to increased secretory capacity of each granulosa cell The multicentric study regroups 128 cases of the ovarian hyperstimulation syndrome ( OHSS ) in in-vitro fertilization ( IVF ) and 256 selected controls . Values of serum oestradiol  obtained from different laboratories were found to be normally distributed after logarithmic transformation . Comparative study of clinical and biological characteristics indicates that among OHSS patients ( i ) mean age was lower ; ( ii ) tubal indications for IVF were less frequent ; ( iii ) polycystic ovary-like conditions ( i.e. hyper and rogenism , anovulation , luteinizing hormone/follicle stimulating hormone ratio > 2 ) were more frequent . OHSS patients displayed ovarian hypersensitivity reflected by higher oestradiol peak concentrations in response to lower dosage of human menopausal gonadotrophin and by a steeper slope of oestradiol increment during stimulation . In these patients , the collection of greater numbers of fertilizable oocytes allowed replacement of more embryos with a good vitality score . Ongoing pregnancy rate was found to be higher among the OHSS patients . The following complications were recorded among OHSS cases : abdominal fluid at echographic examination or clinical ascites ( 86.7 and 71.1 % , respectively ) ; pleural and pericardial effusion ( 21 and 3 % , respectively ) ; haemoconcentration ( 71.1 % ) ; electrolytic disorders ( 6.2 % ) . Although significantly different between groups , clinical and biological parameters under study showed considerable overlap of their distributions in control and OHSS cases . Therefore , these data must be su bmi tted to discriminant analysis in order to derive a formula predictive of the risk of OHSS OBJECTIVE To study the serum levels and correlation of vascular endothelial growth factor ( VEGF ) , insulin-like growth factor 1 ( IGF-1 ) , hormonal profile , and Doppler blood flow changes within the ovarian stroma before and after laparoscopic ovarian drilling ( LOD ) in women with clomiphene-resistant polycystic ovary syndrome ( PCOS ) . DESIGN Prospect i ve controlled study . SETTING University teaching hospital . PATIENT(S ) Twenty-five women with clomiphene-resistant PCOS ( group 1 ) and 20 women with regular menstrual cycles as a comparison group ( group 2 ) . INTERVENTION(S ) Laparoscopic ovarian drilling . MAIN OUTCOME MEASURE(S ) Serum levels of VEGF , IGF-1 , and Doppler indices of ovarian stromal blood flow . RESULT ( S ) The serum levels of VEGF , IGF-1 , T , and LH were significantly higher in group 1 before LOD than in group 2 . The Doppler indices ( pulsatility index and resistance index ) of ovarian stromal blood flow were also significantly lower in group 1 before LOD than in group 2 . The serum levels of VEGF , T , and LH were significantly reduced in group 1 after LOD compared with in group 1 before LOD . Doppler indices ( pulsatility index and resistance index ) of ovarian stromal blood flow were significantly increased after LOD . The VEGF levels before LOD were positively correlated with IGF-1 , LH , and T. After LOD , the VEGF levels were positively correlated with LH and T. CONCLUSION ( S ) Higher serum levels of VEGF and IGF-1 may explain the increased vascularity that was demonstrated by Doppler blood flow measurements in PCOS . Laparoscopic ovarian drilling reduced serum VEGF , IGF-1 , T , and LH and reduced ovarian blood flow velocities , which may explain the reduction of ovarian hyperstimulation syndrome in women with PCOS after LOD OBJECTIVE To evaluate the serum vascular endothelial growth factor concentrations and insulin responses to the oral glucose tolerance test before and after laparoscopic ovarian drilling in women with PCOS . DESIGN Prospect i ve study . SETTING University teaching center . PATIENT(S ) Twenty-seven women with clomiphene citrate-resistant polycystic ovary syndrome . INTERVENTION(S ) Laparoscopic ovarian drilling . MAIN OUTCOME MEASURE(S ) VEGF levels and insulin responses to OGTT before and after ovarian drilling . RESULT ( S ) No difference was found in VEGF levels in women with PCOS before ( 6.0 + /- 1.2 ng/mL ) and after ovarian drilling ( 5.5 + /- 1.2 ng/mL ) . VEGF levels before and after ovarian drilling in women who conceived were , respectively , 5.9 + /- 1.0 and 5.1 + /- 0.9 ng/mL and in those who did not conceive were 6.0 + /- 1.3 and 5.7 + /- 1.2 ng/mL. No correlation was found between baseline serum insulin and VEGF levels . VEGF concentrations in women with normal ovaries ( 4.5 + /- 1.7 ng/mL ) were significantly lower than in women with PCOS . There was no difference in glucose and insulin responses to OGTT before and after ovarian drilling . CONCLUSION ( S ) VEGF levels in women with PCOS are higher than in normal women , and ovarian drilling does not affect these levels . The procedure does not change insulin responses to OGTT The aim of this study was to determine whether follicular oestradiol and vascular endothelial growth factor ( VEGF ) concentrations in women with polycystic ovarian syndrome ( PCOS ) differ according to the use of gonadotrophin-releasing hormone ( GnRH ) antagonists or GnRH agonists . Furthermore , the effect of follicular oestradiol and VEGF concentrations on oocyte and embryo quality was investigated . In this prospect i ve clinical study , 20 women with PCOS undergoing intracytoplasmic sperm injection for male factor infertility were included using a GnRH antagonist or a GnRH agonist protocol . In each follicle , oestradiol and VEGF concentrations were determined . In the GnRH antagonist group 254 follicles and in the GnRH 
    Output:
    
This review concluded that VEGF may have a strategic role in the pathophysiology of PCOS and is the key mediator in the pathogenesis of ovarian hyperstimulation syndrome ( OHSS ) in women undergoing assisted reproductive procedures .