Placenta Growth Factor (PlGF) is a member of the Vascular Endothelial Growth Factor (VEGF) / Platelet-Derived Growth Factor (PDGF) family of growth factors that share a conserved pattern of eight cysteines. PlGF is detected in the placenta, heart, lungs, thyroid, and adipose tissues. These growth factors induce monocyte activation, migration, and production of inflammatory cytokines and VEGF. There are four alternatively spliced PlGF isoforms (PlGF-1, PlGF-2, PlGF-3, and PlGF-4), each with unique secretion patterns and heparin-binding affinities. PlGF-3 is an angiogenic factor, which promotes endothelial cell growth and angiogenesis, being expressed exclusively in the placenta.