Insulin resistance has a key role in the pathogenesis of polycystic ovary syndrome, a common endocrinopathy that affects young women. Therefore, the use of insulin-sensitizing agents has been studied extensively in this patient population. Given the effectiveness of metformin and thiazolidinediones in previous studies, the question arises: is one class better than the other? Grover, A. & Yialamas, M. A. Nat. Rev. Endocrinol. 7, 128-129 (2011); published online 1 February 2011; doi: 10.1038/nrendo.2011.16