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Cited by 194Ovarian function and disordersReproductive Health and TechnologiesReproductive Biology and Fertility

A new era in ovulation induction

Open access
Holzer, Hananel, Casper, Robert, Tulandi, Togas·2006·Fertility and Sterility
DOI 10.1016/j.fertnstert.2005.05.078
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Abstract

Objective To evaluate the efficacy of aromatase inhibitors in ovulation induction, superovulation, and IVF.Design A literature search was conducted with the key words "aromatase inhibitor," "letrozole," "anastrazole," "ovulation induction," "ovulation," and "superovulation" in MEDLINE, EMBASE, and the Cochrane Database of systematic reviews.Result(s) Ovulation induction with letrozole is associated with an ovulation rate of 70%-84% and a pregnancy rate of 20%-27% per cycle. In one study, ovulation and pregnancy rates with letrozole seemed to be higher than those of anastrazole. In superovulation, letrozole is associated with few developing follicles and thick endometrium. The use of letrozole for superovulation is associated with a pregnancy rate higher than with the use of clomiphene citrate (CC) (16.7% vs. 5.6%). The addition of letrozole to FSH treatment leads to a decreased FSH requirement. The pregnancy rate for treatment with letrozole and FSH was similar to that for FSH alone.Conclusion(s) Aromatase inhibitors are as effective as or superior to CC in ovulation induction and in superovulation. Unlike CC, they do not carry an antiestrogenic effect on the endometrium. Given the advantages of aromatase inhibitors, they can be used to replace CC as ovulation-inducing drugs. Their role in IVF remains to be determined.

AI snapshot

Written from the paper’s full text.

TL;DR

This review evaluates third-generation aromatase inhibitors (letrozole, anastrozole) as ovulation-inducing and superovulation agents, concluding they are as effective as or superior to clomiphene citrate (CC) and could replace it as first-line therapy for ovulatory disorders. Their role in IVF remains undetermined.

Key findings

  • Ovulation induction with letrozole yields ovulation rates of 70%–88%, endometrial thickness of 7–9 mm, and pregnancy rates of 20%–27% per cycle, mostly in CC-resistant or thin-endometrium patients (Table 1).
  • In one randomized trial of 49 patients with unexplained infertility, letrozole vs. CC gave fewer follicles (1 vs. 2), thicker endometrium (8.6 mm vs. 6.9 mm), and a trend toward higher pregnancy rate (16.7% vs. 5.6%).
  • Al-Omari et al. found letrozole superior to anastrozole in CC-resistant PCOS: ovulation 84.4% vs. 60%, pregnancy 18.8% vs. 9.7% per cycle, endometrial thickness 8.2 mm vs. 6.5 mm.
  • Adding letrozole to FSH reduces gonadotropin requirement; pregnancy rates were comparable to FSH alone (e.g., 19.1% letrozole/FSH vs. 18.7% FSH-only vs. 10.5% CC/FSH in one study; 21.6% vs. 20.9% in another), though one study reported thinner endometrium with the combination.

Methods

Narrative literature review; MEDLINE, EMBASE, and Cochrane Database searched with keywords "aromatase inhibitor," "letrozole," "anastrazole," "ovulation induction," "ovulation," and "superovulation." Findings are synthesized across identified studies of ovulation induction, superovulation, adjunct gonadotropin therapy, and IVF, with results tabulated (Tables 1–4).

Limitations

The authors state that studies of adjuvant letrozole with gonadotropins are heterogeneous, that patient groups and protocols vary so "firm conclusions cannot be made," and that data on IVF use are sparse. Evident from the text: many cited studies are small (e.g., 7–12 patients), several are nonrandomized or published only as abstracts, and the ideal letrozole dose is explicitly stated to be unknown.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1016/j.fertnstert.2005.05.078

Cites

Statistics

Nothing to recompute.

Claims the paper makes

0 of 98 cited sources checked · 0 supported · 0 flagged

  • Premisecitation

    The use of letrozole for superovulation is associated with a pregnancy rate higher than with the use of clomiphene citrate (CC) (16.7% vs. 5.6%).

    “The use of letrozole for superovulation is associated with a pregnancy rate higher than with the use of clomiphene citrate (CC) (16.7% vs. 5.6%).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [54] Sammour, 2001, Prospective randomized trial comparing the effects of letrozole (LE) and clomiphene citrate (CC) on follicular development, endometrial thickness and pregnancy rate in patients undergoing super-ovulation prior to intrauterine insemination (IUI), Fertil Steril source

      Not checked in the free run.

  • Premisecitation

    The addition of letrozole to FSH treatment leads to a decreased FSH requirement.

    “The addition of letrozole to FSH treatment leads to a decreased FSH requirement.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [61] Mitwally, 2003, Aromatase inhibition reduces gonadotrophin dose required for controlled ovarian stimulation in women with unexplained infertility, Hum Reprod source

      Not checked in the free run.

    • cites [62] Healey, 2004, Effects of letrozole on superovulation with gonadotropins in women undergoing intrauterine insemination, Fertil Steril source

      Not checked in the free run.

    • cites [63] Mitwally, 2004, Aromatase inhibition reduces the dose of gonadotropin required for controlled ovarian hyperstimulation, J Soc Gynecol Investig source

      Not checked in the free run.

  • Premisecitation

    In one study, ovulation and pregnancy rates with letrozole seemed to be higher than those of anastrazole.

    “In one study, ovulation and pregnancy rates with letrozole seemed to be higher than those of anastrazole.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Al-Omari et al. (52) Al-Omari, 2004, Comparison of two aromatase inhibitors in women with clomiphene-resistant polycystic ovary syndrome, Int J Gynaecol Obstet source

      Not checked in the free run.

  • Premisecitation

    The pregnancy rate for treatment with letrozole and FSH was similar to that for FSH alone.

    “The pregnancy rate for treatment with letrozole and FSH was similar to that for FSH alone.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [61] Mitwally, 2003, Aromatase inhibition reduces gonadotrophin dose required for controlled ovarian stimulation in women with unexplained infertility, Hum Reprod source

      Not checked in the free run.

    • cites [62] Healey, 2004, Effects of letrozole on superovulation with gonadotropins in women undergoing intrauterine insemination, Fertil Steril source

      Not checked in the free run.

    • cites [63] Mitwally, 2004, Aromatase inhibition reduces the dose of gonadotropin required for controlled ovarian hyperstimulation, J Soc Gynecol Investig source

      Not checked in the free run.

  • Premisereasoning

    Unlike CC, aromatase inhibitors do not carry an antiestrogenic effect on the endometrium.

    “Unlike CC, they do not carry an antiestrogenic effect on the endometrium.”
    • Also stated in: § AROMATASE INHIBITORS AND OVULATION INDUCTION · plain
      “Unlike CC, aromatase inhibitor does not deplete E receptors or produce a negative effect on the endometrium.”
    Quote in the paperSubstantial claim0 of 7 sources checked
    • cites [8] Gonen, 1990, Sonographic determination of a possible adverse effect of clomiphene citrate on endometrial growth, Hum Reprod source

      Not checked in the free run.

    • cites [9] Eden, 1989, The effect of clomiphene citrate on follicular phase increase in endometrial thickness and uterine volume, Obstet Gynecol

      Not checked in the free run.

    • cites [10] Nakamura, 1997, Effects of clomiphene citrate on the endometrial thickness and echogenic pattern of the endometrium, Fertil Steril source

      Not checked in the free run.

    • cites [11] Yagel, 1992, The effect of ethinyl estradiol on endometrial thickness and uterine volume during ovulation induction by clomiphene citrate, Fertil Steril source

      Not checked in the free run.

    • cites [12] Homburg, 2004, Management of infertility and prevention of ovarian hyperstimulation in women with polycystic ovary syndrome, Clin Obstet Gynecol

      Not checked in the free run.

    • cites [13] Randall, 1991, Cervical mucus score and in vitro sperm mucus interaction in spontaneous and clomiphene citrate cycles, Fertil Steril source

      Not checked in the free run.

    • cites [47] Mitwally, 2004, Aromatase inhibitors in ovulation induction, Semin Reprod Med source

      Not checked in the free run.

  • May combine two claims. 19
  • Classified as probably not a substantial claim. 1
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingcitation

    In a randomized trial of 238 cycles of superovulation in women with idiopathic infertility, pregnancy rates with 7.5 mg letrozole and 100 mg CC daily for 5 days were similar, but the miscarriage rate in the CC-treated cycles was higher.

    “In another randomized trial of 238 cycles of superovulation in women with idiopathic infertility (75), we compared 7.5 mg of letrozole and 100 mg of CC daily for 5 days.The pregnancy rates in both groups were similar, but the miscarriage rate in the CC-treated cycles was higher.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [75] Al Fozan, 2004, A randomized trial of letrozole versus clomiphene citrate in women undergoing superovulation, Fertil Steril source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Ovulation induction with letrozole is associated with an ovulation rate of 70%-84% and a pregnancy rate of 20%-27% per cycle.

    “Ovulation induction with letrozole is associated with an ovulation rate of 70%-84% and a pregnancy rate of 20%-27% per cycle.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [48] Young, 1999, Serum concentrations of enclomiphene and zuclomiphene across consecutive cycles of clomiphene citrate therapy in anovulatory infertile women, Fertil Steril source

      Not checked in the free run.

    • cites [49] Mitwally, 2000, Aromatase inhibition, Reprod Technol

      Not checked in the free run.

    • cites [50] Mitwally, 2001, Use of an aromatase inhibitor for induction of ovulation in patients with an inadequate response to clomiphene citrate, Fertil Steril source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In superovulation, letrozole is associated with few developing follicles and thick endometrium.

    “In superovulation, letrozole is associated with few developing follicles and thick endometrium.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [53] Fisher, 2002, A randomized double-blind comparison of the effects of clomiphene citrate and the aromatase inhibitor letrozole on ovulatory function in normal women, Fertil Steril source

      Not checked in the free run.

    • cites [54] Sammour, 2001, Prospective randomized trial comparing the effects of letrozole (LE) and clomiphene citrate (CC) on follicular development, endometrial thickness and pregnancy rate in patients undergoing super-ovulation prior to intrauterine insemination (IUI), Fertil Steril source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Aromatase inhibitors are as effective as or superior to CC in ovulation induction and in superovulation.

    “Aromatase inhibitors are as effective as or superior to CC in ovulation induction and in superovulation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Clomiphene citrate results in ovulation in most patients (60%-90%), but the pregnancy rates are disappointing (10%-40%).

    “Clomiphene citrate is easy to use and results in ovulation in most patients (60%-90%), but the pregnancy rates are disappointing (10%-40%).”
    Quote in the paperSubstantial claim0 of 4 sources checked
    • cites [4] Franks, 1985, Ovulatory disorders in women with polycystic ovary syndrome, Clin Obstet Gynaecol source

      Not checked in the free run.

    • cites [5] Hull, 1992, The causes of infertility and relative effectiveness of treatment

      Not checked in the free run.

    • cites [6] Kistner, 1965, Induction of ovulation with clomiphene citrate (clomid), Obstet Gynecol Surv source

      Not checked in the free run.

    • cites [7] Adashi, 1984, Clomiphene citrate, Fertil Steril source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Anastrozole and letrozole are selective aromatase inhibitors; they are reversible and highly potent.

    “Anastrozole and letrozole are selective aromatase inhibitors.They are reversible and highly potent.”
    Quote in the paperNot a substantial claim0 of 8 sources checked
    • cites [34] Winer, 2002, American Society of Clinical Oncology technology assessment on the use of aromatase inhibitors as adjuvant therapy for women with hormone receptor-positive breast cancer, J Clin Oncol source

      Not checked in the free run.

    • cites [35] Buzdar, 1996, Anastrozole, a potent and selective aromatase inhibitor, versus megestrol acetate in postmenopausal women with advanced breast cancer, J Clin Oncol source

      Not checked in the free run.

    • cites [36] Marty, 1997, Letrozole, a new potent, selective aromatase inhibitor (AI) superior to aminoglutethimide (AG) in postmenopausal women with advanced breast cancer (ABC) previously treated with anti-estrogens, Proc Am Soc Clin Oncol

      Not checked in the free run.

    • cites [37] Bergh, 1997, Vorozole (Rivizor) versus aminoglutethimide (AG) in the treatment of postmenopausal breast cancer relapsing after tamoxifen, Proc Am Soc Clin Oncol

      Not checked in the free run.

    • cites [38] Dowsett, 1997, Anastrozole—a new generation in aromatase inhibition, Oncology source

      Not checked in the free run.

    • cites [39] Dranitsaris, 2000, Cost-utility analysis of second-line hormonal therapy in advanced breast cancer, Anticancer Drugs source

      Not checked in the free run.

    • cites [40] Sioufi, 1997, Absolute bioavailability of letrozole in healthy post-menopausal women, Biopharm Drug Dispos source

      Not checked in the free run.

    • cites [41] Sioufi, 1997, Comparative bioavailability of letrozole under fed and fasting conditions in 12 healthy subjects after a 25 mg single oral administration, Biopharm Drug Dispos source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Androgens that normally convert to estrogens accumulate in the ovary and increase follicular sensitivity to FSH.

    “In addition, androgens that normally converted to estrogens accumulate in the ovary, and these androgens increase follicular sensitivity to FSH (47).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [47] Mitwally, 2004, Aromatase inhibitors in ovulation induction, Semin Reprod Med source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In a small study of 12 PCOS patients with inadequate response to CC treated with letrozole, 9 (75%) ovulated, 3 conceived, and the mean endometrial thickness was 8.1 mm (6.2 mm with CC).

    “In a small study (50), 12 PCOS patients with inadequate response to CC were treated with letrozole.Of 12 patients, 9 (75%) ovulated, and 3 conceived; the mean endometrial thickness was 8.1 mm (6.2 mm with CC).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [50] Mitwally, 2001, Use of an aromatase inhibitor for induction of ovulation in patients with an inadequate response to clomiphene citrate, Fertil Steril source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Letrozole and anastrazole are completely absorbed after oral administration, with a mean half-life of approximately 45 hours (range, 30-60 hours).

    “Letrozole and anastrazole are completely absorbed after oral administration, with a mean half-life of approximately 45 hours (range, 30 -60 hours).”
    Quote in the paperNot a substantial claim0 of 8 sources checked
    • cites [34] Winer, 2002, American Society of Clinical Oncology technology assessment on the use of aromatase inhibitors as adjuvant therapy for women with hormone receptor-positive breast cancer, J Clin Oncol source

      Not checked in the free run.

    • cites [35] Buzdar, 1996, Anastrozole, a potent and selective aromatase inhibitor, versus megestrol acetate in postmenopausal women with advanced breast cancer, J Clin Oncol source

      Not checked in the free run.

    • cites [36] Marty, 1997, Letrozole, a new potent, selective aromatase inhibitor (AI) superior to aminoglutethimide (AG) in postmenopausal women with advanced breast cancer (ABC) previously treated with anti-estrogens, Proc Am Soc Clin Oncol

      Not checked in the free run.

    • cites [37] Bergh, 1997, Vorozole (Rivizor) versus aminoglutethimide (AG) in the treatment of postmenopausal breast cancer relapsing after tamoxifen, Proc Am Soc Clin Oncol

      Not checked in the free run.

    • cites [38] Dowsett, 1997, Anastrozole—a new generation in aromatase inhibition, Oncology source

      Not checked in the free run.

    • cites [39] Dranitsaris, 2000, Cost-utility analysis of second-line hormonal therapy in advanced breast cancer, Anticancer Drugs source

      Not checked in the free run.

    • cites [40] Sioufi, 1997, Absolute bioavailability of letrozole in healthy post-menopausal women, Biopharm Drug Dispos source

      Not checked in the free run.

    • cites [41] Sioufi, 1997, Comparative bioavailability of letrozole under fed and fasting conditions in 12 healthy subjects after a 25 mg single oral administration, Biopharm Drug Dispos source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    Blocking E production by inhibiting aromatization releases the hypothalamic-pituitary axis from estrogenic negative feedback, increasing FSH secretion and stimulating the development of ovarian follicles.

    “Mitwally and Casper (47) first postulated that blocking E production by inhibiting aromatization would release the hypothalamic-pituitary axis from estrogenic negative feedback.As a result, FSH secretion increases, stimulating the development of ovarian follicles (Fig. 1).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [47] Mitwally, 2004, Aromatase inhibitors in ovulation induction, Semin Reprod Med source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Estrogen exerts a negative feedback on the hypothalamic-pituitary axis and decreases the release of FSH from the pituitary gland.

    “Estrogen exerts a negative feedback on the hypothalamicpituitary axis and decreases the release of FSH from the pituitary gland (42)(43)(44)(45)(46).”
    Quote in the paperSubstantial claim0 of 5 sources checked
    • cites [42] McNeilly, 1988, The control of FSH secretion, Acta Endocrinol Suppl (Copenh)

      Not checked in the free run.

    • cites [43] Kamat, 2002, Mechanisms in tissue-specific regulation of estrogen biosynthesis in humans, Trends Endocrinol Metab source

      Not checked in the free run.

    • cites [44] Naftolin, 1984, Aromatization hypothesis revisited

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    • cites [45] Naftolin, 1988, The cellular effects of estrogens on neuroendocrine tissues, J Steroid Biochem source

      Not checked in the free run.

    • cites [46] Naftolin, 1994, Brain aromatization of androgens, J Reprod Med

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The addition of letrozole to FSH treatment led to a lower FSH requirement without a significant difference in number of follicles >16 mm.

    “However, the addition of letrozole to FSH treatment led to a lower FSH requirement without a significant difference in number of follicles Ͼ16 mm.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [63] Mitwally, 2004, Aromatase inhibition reduces the dose of gonadotropin required for controlled ovarian hyperstimulation, J Soc Gynecol Investig source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In a randomized trial of 49 patients with unexplained infertility, letrozole treatment was associated with a lower E2 level, fewer follicles (1 vs. 2), thicker endometrium (8.6 mm vs. 6.9 mm), and more stromal blood flow compared with CC.

    “Compared with CC, letrozole treatment was associated with a lower E 2 level, fewer follicles (1 vs. 2), thicker endometrium (8.6 mm vs. 6.9 mm), and more stromal blood flow.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [54] Sammour, 2001, Prospective randomized trial comparing the effects of letrozole (LE) and clomiphene citrate (CC) on follicular development, endometrial thickness and pregnancy rate in patients undergoing super-ovulation prior to intrauterine insemination (IUI), Fertil Steril source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In a prospective nonrandomized study, compared with the FSH-only group, the required amount of FSH was significantly lower in the letrozole and FSH and in the CC and FSH groups.

    “Compared with the FSH-only group, the required amount of FSH was significantly lower in the letrozole and FSH and in the CC and FSH groups.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [61] Mitwally, 2003, Aromatase inhibition reduces gonadotrophin dose required for controlled ovarian stimulation in women with unexplained infertility, Hum Reprod source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In Healy et al., patients treated with combined letrozole and gonadotropin required less gonadotropin and developed more follicles >14 mm but had thinner endometrium.

    “Patients treated with a combined regimen required less gonadotropin and developed more follicles Ͼ14 mm but had thinner endometrium.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [62] Healey, 2004, Effects of letrozole on superovulation with gonadotropins in women undergoing intrauterine insemination, Fertil Steril source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In Al-Omari et al., the ovulation rate was 84.4% in the letrozole group and 60% in the anastrazole group.

    “The ovulation rate in the letrozole group was 84.4% and in the anastrazole group was 60%.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [52] Al-Omari, 2004, Comparison of two aromatase inhibitors in women with clomiphene-resistant polycystic ovary syndrome, Int J Gynaecol Obstet source

      Not checked in the free run.

  • May combine two claims. The quote only partly states this claim.

    Interpretationcitation

    These studies suggest that the addition of letrozole to gonadotropins decreases gonadotropin requirements, increases the number of preovulatory follicles, and decreases endometrial thickness without a negative effect on pregnancy rates.

    “These studies suggest that the addition of letrozole to gonadotropins decreases gonadotropin requirements, increases the number of preovulatory follicles, and decreases endometrial thickness without a negative effect on pregnancy rates (Table 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Aromatase inhibitors are orally administered, easy to use, and relatively inexpensive, with minor side effects.

    “They are orally administered, easy to use, and relatively inexpensive, with minor side effects.”
    Quote in the paperNot a substantial claim0 of 8 sources checked
    • cites [34] Winer, 2002, American Society of Clinical Oncology technology assessment on the use of aromatase inhibitors as adjuvant therapy for women with hormone receptor-positive breast cancer, J Clin Oncol source

      Not checked in the free run.

    • cites [35] Buzdar, 1996, Anastrozole, a potent and selective aromatase inhibitor, versus megestrol acetate in postmenopausal women with advanced breast cancer, J Clin Oncol source

      Not checked in the free run.

    • cites [36] Marty, 1997, Letrozole, a new potent, selective aromatase inhibitor (AI) superior to aminoglutethimide (AG) in postmenopausal women with advanced breast cancer (ABC) previously treated with anti-estrogens, Proc Am Soc Clin Oncol

      Not checked in the free run.

    • cites [37] Bergh, 1997, Vorozole (Rivizor) versus aminoglutethimide (AG) in the treatment of postmenopausal breast cancer relapsing after tamoxifen, Proc Am Soc Clin Oncol

      Not checked in the free run.

    • cites [38] Dowsett, 1997, Anastrozole—a new generation in aromatase inhibition, Oncology source

      Not checked in the free run.

    • cites [39] Dranitsaris, 2000, Cost-utility analysis of second-line hormonal therapy in advanced breast cancer, Anticancer Drugs source

      Not checked in the free run.

    • cites [40] Sioufi, 1997, Absolute bioavailability of letrozole in healthy post-menopausal women, Biopharm Drug Dispos source

      Not checked in the free run.

    • cites [41] Sioufi, 1997, Comparative bioavailability of letrozole under fed and fasting conditions in 12 healthy subjects after a 25 mg single oral administration, Biopharm Drug Dispos source

      Not checked in the free run.

  • May combine two claims.

    Interpretationnone given

    The ideal dose of letrozole is unknown; however, it seems that the dose of 5 mg daily for 5 days is the most effective.

    “The ideal dose of letrozole is unknown; however, it seems that the dose of 5 mg daily for 5 days is the most effective.”
    Quote in the paperNot a substantial claim
19 of 19

  • The paper relies on this without support.

    The efficacy of aromatase inhibitors observed in women who failed CC treatment generalizes to women with ovulatory disorders who have not failed CC.

    “Studies evaluating the use of aromatase inhibitors involved mostly women who had failed CC treatment, because of either CC resistance or thin endometrium.”
    “The data on letrozole suggest that it can be used to replace CC as the first-line treatment for women with ovulatory disorders.”
1 of 1

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Conflicting gonadotropin-only cycle counts

    Minor

    The text gives 145 gonadotropin-only cycles for study 62, whereas Table 3 gives 165 cycles for its FSH-alone group.

  • Conflicting patient counts for the Fatemi trial

    Minor

    The narrative calls study 55 a trial of eight patients, while Table 2 lists 15 patients for the same letrozole-versus-CC study.

  • Abstract ovulation-rate range excludes a reported result

    Minor

    The abstract gives a 70%-84% ovulation-rate range for letrozole, but Table 1 reports 88.9% for a letrozole study.

  • Conflicting patient counts for the single-dose study

    Minor

    The same single-dose letrozole study is described as involving seven patients in one section and nine patients in another. Both passages report nine cycles or nine patients, respectively, so these are not interchangeable counts.

4 of 4

The citation lists haven’t been fetched yet

References 79 · Cited by 194

Research works printed but not linked: 5

  1. Goss, 1986, Treatment of advanced postmenopausal breast cancer with the aromatase inhibitor, 4-hydroxyandrostenedione, Cancer Res, 46, 4823
  2. Marty, 1997, Letrozole, a new potent, selective aromatase inhibitor (AI) superior to aminoglutethimide (AG) in postmenopausal women with advanced breast cancer (ABC) previously treated with anti-estrogens, Proc Am Soc Clin Oncol, 16, 156
  3. Bergh, 1997, Vorozole (Rivizor) versus aminoglutethimide (AG) in the treatment of postmenopausal breast cancer relapsing after tamoxifen, Proc Am Soc Clin Oncol, 16, 156
  4. Mitwally, 2000, Aromatase inhibition, Reprod Technol, 10, 244
  5. Al-Fadhli R, Sylvestre C, Buckett W, Tulandi T. A randomized trial of superovulation with letrozole 2.5 mg and 5 mg. Fertil Steril (In Press).

Authors
Holzer, H., Casper, R., & Tulandi, T.
Affiliations
  • McGill University (CA)
  • University of Toronto (CA)
Corresponding author
Tulandi, Togas
ORCID
Venue
Fertility and Sterility
Publisher
Elsevier BV
Published
2006-02
Volume
85
Issue
2
Pages
277-284
ISSN
0015-0282 (ISSN-L)
DOI
10.1016/j.fertnstert.2005.05.078
OpenAlex
W2156723088
Semantic Scholar
3ea624c513feed3406193646aa4d2fa6a41e32ce
Cited by
194
References
79
Citations by year
2026: 3 · 2025: 10 · 2024: 4 · 2023: 13 · 2022: 7 · 2021: 5 · 2020: 10 · 2019: 7 · 2018: 11 · 2017: 10 · 2016: 9 · 2015: 9 · 2014: 16 · 2013: 7 · 2012: 16
FWCI
14.67
Type
journal article
Language
en
Open access
Licence
Locations
  • Fertility and Sterility (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Reproductive Medicine › Ovarian function and disorders
  • Health Sciences › Medicine › Reproductive Medicine › Reproductive Health and Technologies
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Reproductive Biology and Fertility
Keywords
aromatase inhibitors, letrozole, anastrozole, ovulation induction, superovulation, in vitro fertilization, clomiphene citrate, follicle-stimulating hormone, pregnancy rate, endometrial thickness, antiestrogenic effects
MeSH terms
Letrozole, Clomiphene, Drug Therapy, Combination, Female, Fertility Agents, Female, Follicle Stimulating Hormone, Hormones, Humans, Infertility, Female, Nitriles, Ovulation, Ovulation Induction, Pregnancy, Superovulation, Triazoles, Pregnancy Rate, Aromatase Inhibitors

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Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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