Human Placental Growth Hormone Variant in Pathological Pregnancies

Growth hormone (GH), an endocrine hormone primarily secreted from the anterior pituitary, stimulates growth, cell reproduction and regeneration and is a major regulator of postnatal growth. Humans have two GH genes which encode two versions of GH proteins: a pituitary version (GH-N/GH1), and a placental GH variant (GH-V/GH2) which is expressed in the syncytiotrophoblast and extravillous trophoblast cells of the placenta. During pregnancy, placental GH replaces pituitary GH in the maternal circulation at mid-late gestation as the major circulating form of GH. This remarkable change in spatial and temporal GH secretion patterns is proposed to play a role in mediating maternal adaptations to pregnancy. Placental GH is associated with fetal growth and its circulating concentrations have been investigated across a range of pregnancy complications. However, progress in this area has been hindered by a lack of readily accessible and reliable assays for measurement of placental GH. This review will discuss the potential roles of placental GH in normal and pathological pregnancies and will touch on the assays used to quantify this hormone.