There are many hormones that play a role in both women’s and men’s reproductive biology. The correct hormones at the correct time with the correct concentration is necessary to achieve pregnancy and a healthy gestation. Men require adequate testosterone, FSH, and LH for sperm production. Women need appropriate concentrations, and at the right time of their cycle, of FSH, LH, estrogen, and progesterone to facilitate egg maturation and endometrial growth for implantation. Problems with regulating reproductive hormones are observed in ~25% of IVF cases.