title: Aromatase inhibition reduces gonadotrophin dose required for controlled ovarian stimulation in women with unexplained infertility.
abstract: BACKGROUND
  Adding clomiphene citrate (CC) to FSH for controlled ovarian stimulation (COS) decreases FSH dose required for optimum stimulation. However, because of its anti-estrogenic effects, CC may be associated with lower pregnancy rates offsetting the FSH-dose reduction benefit. Previously, we reported the success of aromatase inhibition in inducing ovulation without antiestrogenic effects.
  
  
  METHODS
  A prospective pilot study that included women with unexplained infertility undergoing COS and intrauterine insemination. Thirty-six women received the aromatase inhibitor letrozole + FSH, 18 women received CC + FSH and 56 women received FSH only. Each woman received one treatment regimen in one treatment cycle. All patients were given recombinant or highly purified FSH (50-150 IU/day) starting on day 3 to 7 until day of hCG.
  
  
  RESULTS
  The FSH dose needed was significantly lower in letrozole + FSH and CC + FSH groups compared with FSH-only without a difference in number of follicles >1.8 cm. Pregnancy rate was 19.1% in the letrozole + FSH group, 10.5% in the CC + FSH group and 18.7% in the FSH-only group. Both pregnancy rate and endometrial thickness were significantly lower in CC + FSH group compared with the other two groups. Estradiol (E2) levels were significantly lower in the letrozole + FSH group compared with the other two groups.
  
  
  CONCLUSIONS
  Similar to CC, aromatase inhibition with letrozole reduces FSH dose required for COS without the undesirable antiestrogenic effects sometimes seen with CC.
authors.affiliation: Samuel Lunenfeld Research Institute and Mount Sinai Hospital, Reproductive Sciences Division, Department of Obstetrics & Gynecology, University of Toronto, Toronto, Canada.
authors.forename: M F M
authors.initials: MF
authors.lastname: Mitwally
authors.forename: R F
authors.initials: RF
authors.lastname: Casper
mesh_terms: D000328:Adult; D047072:Aromatase Inhibitors; D002996:Clomiphene / Q000008:administration & dosage; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D004958:Estradiol / Q000097:blood; D005260:Female; D005300:Fertility Agents, Female / Q000008:administration & dosage; D043373:Follicle Stimulating Hormone, Human / Q000008:administration & dosage*; D006801:Humans; D007247:Infertility, Female / Q000097:blood / Q000000981:diagnostic imaging / Q000188:drug therapy*; D000077289:Letrozole; D007986:Luteinizing Hormone / Q000097:blood; D009570:Nitriles / Q000008:administration & dosage; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000187:drug effects; D010062:Ovulation Induction / Q000379:methods*; D010865:Pilot Projects; D011247:Pregnancy; D011446:Prospective Studies; D014230:Triazoles / Q000008:administration & dosage; D014463:Ultrasonography
chemical_list: D047072:Aromatase Inhibitors; D004791:Enzyme Inhibitors; D005300:Fertility Agents, Female; D043373:Follicle Stimulating Hormone, Human; D009570:Nitriles; D014230:Triazoles; D002996:Clomiphene; D004958:Estradiol; D000077289:Letrozole; D007986:Luteinizing Hormone