After an initial 6 - 8 weeks of metformin , they received either letrozole ( 2.5 mg ) or clomiphene ( 100 mg ) from day 3 - 7 of their menstrual cycle .
Efficacy of combined metformin-letrozole in comparison with metformin-clomiphene citrate in clomiphene-resistant infertile women with polycystic ovarian disease. Adding metformin to clomiphene citrate in clomiphene-resistant polycystic ovary syndrome (PCOS) patients increases ovulatory response. However, because of anti-estrogenic effects of clomiphene it may be associated with lower pregnancy rate, offsetting the ovulation rate benefit. letrozole is an aromatase inhibitor which induces ovulation without anti-estrogenic effects. ### methods Infertile women with PCOS were randomly divided into metformin-letrozole (29 patients) and metformin-clomiphene groups (30 patients). After an initial 6 - 8 weeks of metformin , they received either letrozole ( 2.5 mg ) or clomiphene ( 100 mg ) from day 3 - 7 of their menstrual cycle . Estradiol (E2) levels, number of follicles, pregnancy rates and endometrial thickness were measured on the day of HCG administration. ### results Mean total E2 and E2 per mature follicle were significantly higher in clomiphene group without a difference in mean number of mature follicles >18 mm and ovulation rate. Endometrial thickness was significantly higher in letrozole group. The pregnancy rate in letrozole group (10 patients, 34.50%) as compared with clomiphene group (5 patients, 16.67%) did not show significant difference, whereas full-term pregnancies were higher in letrozole group [10 patients (34.50%) versus 3 patients (10%)]. ### conclusion In clomiphene-resistant PCOS patients, the combination of letrozole and metformin leads to higher full-term pregnancies.
### Instruction:
            Given the context about compound efficacy for the given treatment mentioned within the input, mentioned the compounds 
            that can co-occur for the mentioned treatment

            ### Input:
            Efficacy of combined metformin-letrozole in comparison with metformin-clomiphene citrate in clomiphene-resistant infertile women with polycystic ovarian disease. Adding metformin to clomiphene citrate in clomiphene-resistant polycystic ovary syndrome (PCOS) patients increases ovulatory response. However, because of anti-estrogenic effects of clomiphene it may be associated with lower pregnancy rate, offsetting the ovulation rate benefit. letrozole is an aromatase inhibitor which induces ovulation without anti-estrogenic effects. ### methods Infertile women with PCOS were randomly divided into metformin-letrozole (29 patients) and metformin-clomiphene groups (30 patients). After an initial 6 - 8 weeks of metformin , they received either letrozole ( 2.5 mg ) or clomiphene ( 100 mg ) from day 3 - 7 of their menstrual cycle . Estradiol (E2) levels, number of follicles, pregnancy rates and endometrial thickness were measured on the day of HCG administration. ### results Mean total E2 and E2 per mature follicle were significantly higher in clomiphene group without a difference in mean number of mature follicles >18 mm and ovulation rate. Endometrial thickness was significantly higher in letrozole group. The pregnancy rate in letrozole group (10 patients, 34.50%) as compared with clomiphene group (5 patients, 16.67%) did not show significant difference, whereas full-term pregnancies were higher in letrozole group [10 patients (34.50%) versus 3 patients (10%)]. ### conclusion In clomiphene-resistant PCOS patients, the combination of letrozole and metformin leads to higher full-term pregnancies.

            ### Response:
            metformin, letrozole, clomiphene
            