In the last 50 years, sperm counts in men have declined by over 50% demonstrating a male fertility crisis. Moreover, reproductive failure is a major constraint to the efficiency of livestock production. The broad focus of my research program is elucidating the biology of male reproduction and endocrinology. More specifically, we study the development and function of the mammalian testis, especially Leydig cells which produce steroid hormones that are critical for reproductive success. In my lab, we are investigating physiological, cellular, and molecular factors involved in Leydig function using murine and porcine models. A deeper understanding of the factors that affect Leydig cell function is essential to the development of novel therapies or intervention strategies to maximize fertility in both animals and humans.