There's a hormone called human chorionic gonadotrophin or hCG, which is produced by the developing embryo when women get pregnant. hCG helps control and regulate other development hormones. Because it appears so early into the pregnancy, it's used as an early indicator of pregnancy by over-the-counter pregnancy tests (the ones you pee on).
However, some types of cancer, including testicular cancer, also produce hCG. This means that if men pee on that same pregnancy stick, and test positive, it might be an indicator that they have developed testicular cancer! This puts the Arnold Schwarzenegger movie "Junior" in a completely different perspective!