Polycystic ovary syndrome (PCOS) is one of the most common endocrinopathies, affecting 5% to
10% of women of reproductive age. Women with PCOS suffer from anovulatory infertility.
Following lifestyle modification with weight reduction in obese PCOS women, clomifene citrate
(CC) is considered the first line treatment for ovulation induction (OI) in these women.
75-80% of women will ovulate after CC administration. However, there is a discrepancy between
the ovulation rate and pregnancy rate, which was reported to be 22% per each ovulating cycles
after CC. Other alternatives, including gonadotropin injections and laparoscopic ovarian
drilling, carried different disadvantages, such as costly treatment and risks of ovarian
hyperstimulation syndrome and multiple pregnancy rate in gonadotrophin therapy and surgical
risks and risk of ovarian failure in surgical treatment.
The use of aromatase inhibitor, letrozole (LTZ), in reproductive medicine started in 2001.
After this publication, there have been many groups of investigators studying the use of LTZ
either in OI or ovarian stimulation in IVF cycles. A large multicentre randomized trial
reported a significantly higher ovulation rate and live-birth rate comparing LTZ with CC. In
majority of the publications, the multiple pregnancy rate was lower in LTZ group than in CC
group. This can be attributed to the higher chance of monofollicular development after LTZ
compared with CC. However, there is no information comparing the hormonal profile and
follicular development after letrozole and CC.
Mild ovarian stimulation using LTZ or CC in conjunction with intrauterine insemination is
commonly offered to ovulatory women with unexplained infertility, minimal endometriosis or
mild factor to improve the pregnancy rate. There is again no information comparing the
hormonal profile and follicular development after letrozole and CC in ovulatory women.
The aim of this study is to compare the hormonal profile after the use of LTZ and CC in
anovulatory PCOS women and ovulatory women with unexplained subfertility. The hypothesis is
that the FSH risk after LTZ is shorter than that of CC.