metformin in polycystic ovary syndrome (PCOS)

Last reviewed 09/2022

  • women with polycystic ovary syndrome (PCOS) have markedly decreased insulin sensitivity - there is therefore an increased rate of both impaired glucose intolerance and frank diabetes in women with PCOS. There is also an increased incidence of insulin resistance and body mass index in women with PCOS
  • Moghetti et al (1) undertook a double-blind trial comparing the effects of metformin with placebo in women with PCOS. This trial revealed that:
    • metformin significantly improved the frequency of menstruation, increased insulin sensitivity and reduced serum testosterone and insulin
    • there was no significant difference in BMI between the two groups
  • there is evidence that metformin used alone or combined with clomifene is effective for improving ovulation rates in women with polycystic ovary syndrome
    • a systematic review and meta-analysis was undertaken (2,3)
      • 15 randomised controlled trials were included
      • the duration of trials ranged from 4-44 weeks - median 10 weeks
      • metformin improved ovulation rate (46% metformin; 24% placebo) at median 10 weeks; NNT 5 (4 to 8)
      • metformin reduced systolic blood pressure (weighted mean difference -9mmHg, 95% CI -15 to -3), and reduced diastolic blood pressure (weighted mean difference - 6mmHg, CI-10 to -2)
      • metformin plus clomifene improved ovulation and clinical pregnancy rates more than clomifene alone
        • ovulation rate at median 10 weeks (76% metformin + clomifene; 42% clomifene alone); NNT 4 (2 to 17)
        • clinical pregnancy rate at median 10 weeks (32% metformin + clomifene; 7% clomifene alone); NNT 5 (3 to 8)

  • however, there is no evidence that metformin improves live birth rates whether it is used alone or in combination with clomiphene, or when compared with clomiphene (4)

  • a further systematic review concluded (5):
    • clomiphene alone is superior to metformin alone regarding live birth rate and ovulation. The combination (clomiphne+metformin) is superior to clomiphne alone as a primary method for ovulation induction and to achieve pregnancy in PCOS. However, when addressing live birth rate, no statistically significant difference could be demonstrated. Because of the side effects profile and contraindications of metformin, the authors stated that metformin should not be indicated as a primary ovulation induction agent in women with PCOS.