INTRODUCTION
Polycystic Ovary Syndrome (PCOS) is the most common condition that leads to anovulatory infertility in women. There has been a significant increase in the number of women that present with PCOS and leading to increased scientific examination towards understanding the syndrome.
The syndrome has several clinical manifestations, and anovulatory infertility is one of the most common.
Letrozole is an aromatase inhibitorhas been widely used for ovulation induction. Letrozole prevents the conversion of androgen to oestrogen by inhibiting aromatase activity. This releases the negative feedback effect of oestrogen on the hypothalamus and pituitary leading to release of gonadotrophins; causing follicular growth and subsequent ovulation. It does not have any adverse effects on the fetus and is safe.(7,8) Recently , letrozole has been suggested by ESRHE as the first line for ovulation induction in polycystic ovarian syndrome patients.
The addition of an ovulatory dose of human chorionic gonadotropin (HCG) has been used as an adjuvant to letrozole treatment to trigger ovulation.(10) When size of pre-ovulatory follicle reaches to 18-20 mm. HCG has similar activity to LH and binds to its receptor. Ovulation occurs 38-40 hours after a single HCG injection (10,000 IU IM) . The remaining parts of the dominant follicle transforms into Corpus luteum. It continues to grow during the luteal phase and produce significant amounts of hormones , particularly progesterone and to lesser extent estrogen and inhibin. Progesterone plays a vital role in making endometrial receptive to implantation of blastocyst and supportive of early pregnancy.