***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: OBJECTIVES : To compare the efficacy of letrozole and clomiphene citrate ( CC ) in patients of anovulatory polycystic ovarian syndrome ( PCOS ) with infertility . MATERIAL S AND METHODS : This prospect i ve r and omized clinical trial included 204 patients of PCOS . 98 patients ( 294 cycles ) received 2.5–5 mg of letrozole ; 106 patients ( 318 cycles ) received 50–100 mg of CC ( both orally from Days 3–7 of menstrual cycle ) . The treatment continued for three cycles in both the groups . Main outcome measures : ovulation rate , endometrial thickness , and pregnancy rate . Statistical analysis was done using SPSS 13 software . P value less than 0.05 was considered significant . RESULTS : The mean number of dominant follicles in letrozole groups and CC groups was 1.86±0.26 and 1.92±0.17 , respectively ( P=0.126 ) . Number of ovulatory cycle  in letrozole group was 196 ( 66.6 % ) versus 216 ( 67.9 % ) in CC group ( P=0.712 ) . The mean mid-cycle endometrial thickness was 9.1±0.3 mm in letrozole group and 6.3±1.1 in CC group , which was statistically significant ( P=0.014 ) . The mean Estradiol [ E2 ] level  in clomiphene citrate group was significantly higher in CC group ( 364.2±71.4 pg/mL ) than letrozole group ( 248.2± 42.2 pg/mL ) . 43 patients from the letrozole group ( 43.8 % ) and 28 patients from the CC group ( 26.4 % ) became pregnant . CONCLUSION : Letrozole and CC have comparable ovulation rate . The effect of letrozole showed a better endometrial response and pregnancy rate compared with CC Objective : To compare the pregnancy outcomes achieved by in vitro fertilization ( IVF ) between minimal stimulation and conventional antagonist protocol s in poor ovarian responders ( PORs ) . Material s and methods : In this r and omized controlled trial , 77 PORs undergoing IVF were selected and divided into two groups . First group was the minimal stimulation group ( n = 42 ) receiving 100 mg/day clomiphene citrate on day 2of the cycle for 5 day that was followed by150IU/day human menopausal gonadotropin ( hMG ) on day 5 of the cycle . Second group was the conventional group ( n = 35 ) receiving at least 300 IU/daygonadotropin on day 2 of the cycle . Gonadotropin-releasing hormone ( GnRH ) antagonist protocol was applied for both groups according to flexible protocol . Number of retrieved oocytes and chemical pregnancy rate were the main outcomes . Results : There was no difference in number ofretrieved oocyte and pregnancy rate ( 2.79 ± 1.96 vs. 2.20 ± 1.71 and 5.6 % vs. 4.1 % ; p > 0.05 ) between both groups . The gonadotropin dose used in the minimal stimulation group was lower than conventional group ( 1046 ± 596 vs. 2806 ± 583 ) . Conclusion : Minimal stimulation protocol with lower gonadotropin used is likely to be considered as a patient- friendly and cost-effective substitute for PORs BACKGROUND Use of letrozole , a selective inhibitor of aromatase , reduces the gonadotrophin dose required to induce follicular maturation . We evaluated whether incorporation of letrozole could be an effective low-cost IVF protocol for poor responders . METHODS A r and omized , controlled , single-blind trial was conducted in the Assisted Reproduction Unit , Institute of Reproductive Medicine , Kolkata , India . Thirty-eight women with a history of poor ovarian response to gonadotrophins were recruited . Thirteen women ( Let-FSH group ) received letrozole 2.5 mg daily from day 3 - 7 , and recombinant FSH ( rFSH ) 75 IU/day on days 3 and 8 ; and 25 women ( GnRH-ag-FSH group ) underwent long GnRH agonist protocol and stimulated with rFSH ( 300 - 450 IU/day ) . Ovulation was triggered by 10,000 IU of HCG followed by IVF-embryo transfer . The main outcome measures were total dose of rFSH ( IU/cycle ) , terminal estradiol ( E2 ) ( pg/ml ) , numbers of follicles , oocytes retrieved and transferable embryo , endometrial thickness ( mm ) , and pregnancy rate . RESULTS Compared with the GnRH-ag-FSH group ( 2865 + /- 228 IU ) , the Let-FSH group ( 150 + /- 0 IU ) received a significantly ( P < 0.001 ) lower total dose of FSH .  Except for terminal E2 , which was significantly higher ( P < 0.001 ) in the GnRH-ag-FSH group ( 380 + /- 46 pg/ml ) than the Let-FSH group ( 227 + /- 45 pg/ml ) , the treatment outcomes in all other respects , including pregnancy rate , were statistically comparable . CONCLUSIONS Adjunctive use of letrozole may form an effective means of low-cost IVF protocol in poorly responding women Background This large prospect i ve , r and omized study was design ed to compare the “ mild ” protocol with clomiphene citrate , low-dose gonadotropins and a GnRH-antagonist ( CC/Gn/GnRH-ant protocol ) with the “ long ” protocol with a GnRH-agonist and high-dose Gn for the controlled ovarian hyperstimulation ( COH ) of patients with expected poor ovarian responsiveness undergoing IVF . Material s and Methods A total of 695 women with clinical , endocrine and ultrasound characteristics suggesting a low ovarian reserve and a poor responsiveness to COH were recruited and r and omly assigned to receive the CC/Gn/GnRH-ant “ mild ” protocol ( mild group , n = 355 ) or the “ long ” protocol with high-dose Gn ( long group , n = 340 ) . Results The “ mild ” stimulation led to significantly shorter follicular phase , lower consumption of exogenous Gn and lower peak estradiol level than the “ long ” regimen . With the “ long ” protocol , significantly less cycles were cancelled due to the lack of ovarian response ; further , it obtained significantly more oocytes , more mature oocytes , more embryos , and a thicker endometrium . As for the final IVF outcome , however , the two stimulation regimens obtained comparable implantation rate , clinical pregnancy rate , and ongoing pregnancy rate at 12 weeks . Conclusions In conclusion , the “ mild ” CC/Gn/GnRH-ant stimulation protocol is a valid alternative to the long protocol with high Gn dose as it obtains a comparable success rate and requires significantly less medications , with an obvious economical advantage OBJECTIVE The aim of this r and omized controlled trial ( RCT ) was to investigate whether IVF outcomes would differ between patients with POR who received three different gonadotropin doses with or without the addition of  letrozole during ovulation stimulation . STUDY DESIGN Only those who fulfilled two of the three Bologna criteria were included to the study . 95 patients met the inclusion criteria and agreed to participate in the study . In the first group , 31 patients were treated with 450IU gonadotropins . In the second group , 31 patients were treated with 300IU gonadotropins . The third group comprised 33 patients and was treated with 150IU gonadotropins in combination with letrozole . RESULTS The results indicate that differences in doses of hMG and rFSH in patients with POR result in a similar number of retrieved MII and fertilized oocytes , similar fertilization rates , number of transferred embryos , implantation , cancelation , chemical , clinical , and ongoing pregnancy rates . CONCLUSIONS Increasing the dose of gonadotropins during ovulation stimulation is an intuitively appealing approach when the patient is a poor responder . However , increasing the dose does not necessarily improve the reproductive outcome . Using a mild stimulation with addition of letrozole was as effective as stimulation with higher doses of gonadotropins alone in this patient population OBJECTIVE Poor responders represent a frustrating condition for couples undergoing IVF and clinicians , and their treatment remains disputed . To assess the efficacy and the most suitable protocol , we conducted a r and omized controlled trial comparing three different protocol s of ovarian stimulation in poor responder women :  clomiphene citrate ( CC ) plus a high dose of gonadotropins and GnRH antagonist , flexible GnRH antagonist protocol and a short GnRH agonist protocol . PATIENTS AND METHODS Between July 2014 and December 2015 we enrolled 250 poor responders in a previous IVF cycle at least 3 months before . We divided into three groups : group A , 68 women treated with clomiphene citrate and FSH plus antagonist ; Group B , 71 patients treated with FSH plus antagonist ; Group C , 75 patients treated with FSH plus GnRH agonist .  RESULTS The GnRH agonist protocol showed a significantly higher pregnancy rate ( 29.3 % vs. 5.9 % vs. 14.1 % respectively ) than the clomiphene and the GnRH antagonist protocol , number of mature oocytes collected , estradiol levels and endometrial thickness . The cost of medications for each baby born was lower for the GnRH agonist protocol than for the others ; the implantation rate was significantly lower in the clomiphene group ( 4.8 % ) than in the GnRH antagonist group ( 9.3 % ) and the GnRH agonist groups ( 19.2 % ) . No significant differences emerged for total FSH administered , days of stimulation , numbers of oocytes retrieved and embryos transferred . CONCLUSIONS This study demonstrates that short GnRH agonist protocol should be the first choice in poor responders ; instead , clomiphene citrate should be avoided due to its very low success rate and high costs Twenty-four healthy adult female volunteers participated in a r and omized , three-phase double-blind crossover trial comparing the single-dose ( 50 mg ) pharmacokinetics of three formulations of clomiphene citrate ( CC ) .  Plasma levels of both the Z(cis ) and E(trans ) isomers of  CC  , as well as principal metabolites , were determined at periodic intervals ; and no differences between formulations were observed . The active Z isomer attained peak blood levels later than the inactive E isomer and was eliminated much more slowly , significant plasma concentrations still being detected up to 1 month after treatment . The results of this study demonstrate that three commercially available formulations of CC are bioequivalent This study evaluates the efficacy of a stimulation protocol with clomiphene citrate (CC)/human menopausal gonadotropin (hMG)/cetrorelix and its effects on oocyte quality and endometrium .  One hundred and twenty couples with male-factor infertility who were about to undergo their first intracytoplasmic sperm injection cycles were r and omized into two groups . Sixty women were stimulated with the CC/hMG/cetrorelix protocol ( cetrorelix group ) and 60 received the buserelin long protocol ( buserelin group ) . Fewer oocytes were recovered in the cetrorelix group than in the buserelin group ( mean ± st and ard deviation ( SD ) : 11.1 ± 4.0 vs. 17.3 ± 5.8 , p < 0.001 ) ; however , the percentages of metaphase II , metaphase I and germinal vesicle oocytes were similar between the two groups . Serum estradiol level was significantly lower in the cetrorelix than in the buserelin group ( mean ± SD : 2600.58 ± 1189.11 vs. 3293.46 ± 1221.49 pg/ml , p = 0.006 ) , but the endometrial thickness was similar . The implantation rates ( 19.2 % vs. 17.7 % ) and the pregnancy rates ( 41.7 % vs. 40.0 % ) were similar between groups . The ampoules ( mean ± SD : 18.9 ± 3.0 vs. 38.9 ± 12.2 , p < 0.001 ) and injections ( mean ± SD : 6.8 ± 1.1 vs. 15.7 ± 3.1 , p < 0.001 ) of gonadotropin used were significantly lower in the cetrorelix group than in the buserelin group . No patients in either group developed a premature luteinizing hormone surge . The present study found no statistically significant difference between the two treatment modalities with regard to pregnancy rates In an attempt to improve the pregnancy rate following in vitro fertilization and embryo transfer by increasing the numbers of embryos available for transfer to each patient , a prospect i ve , r and omized comparison of clomiphene citrate alone ( 50 mg/day , cycle days 5 to 9 ) with the combination of clomiphene as above plus human menopausal gonadotropin ( 2 ampules/day , cycle days 6 , 8 , and 10 ) was undertaken from January 
    Output:
    
We found no conclusive evidence indicating that clomiphene citrate or letrozole with or without gonadotropins differed from gonadotropins in GnRH agonist or antagonist protocol s with respect to their effects on live-birth or pregnancy rates , either in the general population of women undergoing IVF treatment or in women who were poor responders .
Use of clomiphene or letrozole led to a reduction in the amount of gonadotropins required and the incidence of OHSS .
However , use of clomiphene citrate or letrozole may be associated with a significant increase in the incidence of cycle cancellations , as well as reductions in the mean number of oocytes retrieved in both the general IVF population and the poor responders .