Abstract: Objective：To investigate the effect of letrozole on matrix metalloproteinases-2（MMP-2） and tissue
inhibitor of metalloproteinase-2（TIMP-2） in the patients with uterine fibroids. Methods：Forty patients with uterine fibroids were divided into two groups. Treatment group patients were received myomectomy after treatment with letrozole tablets（2.5 mg/day） for three course of treatment. Control group were only received myomectomy. The volume of uterus and uterine fibroids were measured through B-mode ultrasonography. The expression of MMP-2 and TIMP-2 in uterine smooth muscle and uterine fibroids were detected by Real-time PCR and Western Blot. Results：Compared with control group and in the treatment group，the clinical symptom was significantly improved， the level of estradiol was significantly decreased， the volume of uterus and uterine fibroids were markedly diminished，the expression of MMP-2 in uterine smooth muscle and uterine fibroids was significantly decreased，the expression of TIMP-2 in uterine smooth muscle and uterine fibroids was markedly increased in the letrozole group. Conclusions：Letrozole diminishs the size of uterine fibroids in human，the mechanism which of may be related to the decrease of estradiol and MMP-2 expression and the increase of TIMP-2 expression induced by letrozole.

Key words: Letrozole, Myometrium, Leiomyoma, Matrix metalloproteinase 2, Tissue inhibitor of metalloproteinase-2