Study On The Effects of Letrozole And Clomiphene Citrate For Induction of Ovulation In Polycystic Ovarian Syndrome(PCOS)

Polycystic Ovarian Syndrome (PCOS) is the most common endocrinopathy among women of reproductive age group and is one of the leading causes of infertility. It is characterized by chronic anovulation and hyperandrogenism with variable clinical manifestations that include oligomenorrhea, infertility, hirsutism, and acne (Ehrmann DA 2005).

Several methods have been described to induce ovulation in PCOS patients- weight reduction, laparoscopic ovarian drilling and the use of various induction ovulation agents like clomiphene citrate (CC), aromatase inhibitors (AIs) and gonadotrophins.

Clomiphene citrate (CC) has been most widely used and standard drug for the treatment of infertility. It is known that clomiphene citrate results in an ovulation rate of 60-85%, but a conception rate of only around 20% (Bayar et al 2006, Sohrabvand et al 2006). About 20-25% of women are resistant to CC and do not ovulate. Discrepancy between ovulation and pregnancy rate is related to anti-estrogenic activity on endometrium and cervical mucus is due to CC has a long half life of 5 to 7 days.

In view of disappointing result of CC treatment with many adverse effect and cost and possible complication of gonadotrophin, the concept of aromatase inhibition was proposed as a new method of ovulation that are easy to use, less expensive and more effective drugs.

Letrozole is an oral, potent, reversible, and highly selective aromatase inhobitor that prevent androgen-to-estrogen (E) conversion. These aromatase inhibitors have a short half life (45 hours), hence is rapidly eliminated from the body. No adverse effect on E target tissues is seen with letrozole due to this short half life; furthermore, it does not down regulate the ER compare to CC.