{Reference Type}: Journal Article {Title}: A Modified Technique for Inducing Polycystic Ovary Syndrome in Mice. {Author}: Zhou B;Guo F;Long Y;She J;Gao L;Huang H; {Journal}: J Vis Exp {Volume}: 0 {Issue}: 209 {Year}: 2024 Jul 5 {Factor}: 1.424 {DOI}: 10.3791/66637 {Abstract}: Polycystic ovary syndrome (PCOS) is one of the leading causes of infertility in women. Animal models are widely used to study the etiologic mechanisms of PCOS and for related drug development. Letrozole-induced mouse models replicate the metabolic and reproductive phenotypes of patients with PCOS. The traditional method of letrozole treatment in PCOS mice requires daily dosing over a certain period, which can be labor-intensive and cause significant stress to the mice. This study describes a simple and effective method for inducing PCOS in mice by implanting a controlled letrozole-releasing mini-pump. A mini-pump capable of stable, continuous release of a quantitative amount of letrozole was fabricated and implanted subcutaneously in mice under anesthesia. This study demonstrated that the mouse model successfully mimicked PCOS features after letrozole mini-pump implantation. The materials and equipment used in this study are readily available to most laboratories, requiring no special customization. Collectively, this article provides a unique, easy-to-perform method for inducing PCOS in mice.