Following her ScD, Platz joined the faculty at Johns Hopkins University as an assistant professor in the Department of Epidemiology in 1999.[2] While serving in this role, she started the Hormones in Umbilical Cord Blood Study (HUB) to evaluate whether umbilical cord blood hormone and growth factor concentrations differ by race.[3] Platz also co-led a 10-year study of more than 30,000 health professionals that found the longer men take cholesterol-lowering drugs, the far less likely they were to develop advanced prostate cancer.[4] In 2008, Platz was appointed co-director of the Cancer Prevention and Control Program at the Sidney Kimmel Comprehensive Cancer Center.[5]