BACKGROUND: Metformin, an insulin-sensitizing agent, has been used successfully 
as the first-line drug to induce ovulation in women with polycystic ovary 
syndrome. There are, however, very few studies evaluating metformin treatment in 
women with clomiphene citrate (CC)-resistant polycystic ovaries (PCO).
METHODS: Twenty infertile Chinese women aged <40 years, who had ultrasound 
features of PCO and remained anovulatory on CC, were randomized by computer 
using the sealed envelope method to receive placebo or metformin 500 mg three 
times a day for 3 months. Hormonal and metabolic profiles were determined before 
the therapy and were repeated after 3 months for women who failed to become 
pregnant within this period. Clomiphene was then added for one cycle to those 
women who did not ovulate after taking placebo or metformin alone.
RESULTS: The median ovulation rate in the placebo group was 0% (range: 0--50%) 
after placebo only and 6.9% (range: 0--50%) after placebo and CC, whereas the 
corresponding rates in the metformin group were 0% (range: 0--22%) and 0% 
(range: 0--22%) respectively. There was no improvement in the ovulation rate 
despite a significant reduction of body mass index, serum testosterone and 
fasting leptin concentrations in the metformin group.
CONCLUSIONS: Metformin treatment may result in successful ovulation only in 
certain subgroups of these women.