Summary:
Anovulation accounts for around 20% cases of infertility
even when other fertility factors are normal. Clomiphene
Citrate (CC), the oral anti-estrogen has long been used as
the first line drug for induction of ovulation. Clomiphene
is associated with a high ovulation (60-80%) but relatively
poor pregnancy rate (30-40%). CC leads to long lasting
estrogen receptor depletion. Because of its long half-life
(2 weeks), CC possibly exerts a negative feedback effect on
the cervical mucous and endometrial development with
subsequent implantation failure. The aromatase inhibitor
letrozole (originally approved for use in postmenopausal
women with breast cancer to suppress estrogen