ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of two different doses of letrozole in promoting ovulation in infertile women with polycystic ovarian syndrome (PCOS).</p><p><b>METHODS</b>Seventy-six PCOS infertile women undergoing intrauterine insemination (IUI) or with anovulation were divided into two groups and received oral letrozole at the daily dose of 2.5 (n=36) or 5.0 mg (n=40) from the 3rd to the 7th day of the menstrual cycle. Three days after discontinuation of the medication (the 10th day of the menstrual cycle ), ultrasound scanning was performed to monitor the follicle development. When the diameter of the biggest follicle reached 14 mm, the presence of luteinizing hormone (LH) was monitored; when LH positivity was detected, blood samples were drawn to test follicle-stimulating hormone (FSH), LH, estradiol (E2) and testosterone (T) levels. Human chorionic gonadotropin (hCG, 10 000 U) was then injected to induce ovulation.</p><p><b>RESULTS</b>The ovulation rate, stimulation follicle days, diameter of the biggest follicle on the day of LH positivity and the thickness of endometrium were all similar between the two groups (P>0.05). But in women receiving 5.0 mg letrozole, both the number of mature follicles and pregnancy rate were significantly higher than those in women having the half dose (P<0.05). The levels of FSH, LH, E2, and T on the third day of menstruation and on the day of HCG injection were similar between the two groups (P<0.05).</p><p><b>CONCLUSION</b>Letrozole at the dose of 5.0 mg/day produces higher pregnancy rate and more mature follicles in fertile women with PCOS.</p>