CLINICAL COUNTERPOINT - THE PHYSIOLOGY OF PLACENTAL-LACTOGEN IN HUMAN-PREGNANCY

Placental lactogen (PL), a protein hormone synthesized and secreted by the placenta, has striking homologies in its chemical and biological properties to GH and PRL (1, 2) (Table 1). As discussed in the accompanying paper by Saunders and co-workers (3), considerable information is available about the chemistry of human (h) PL and the molecular biology of the hPL/hGH gene family. Much less is known about the biological actions of hPL during pregnancy, the mechanisms by which hPL exerts its biological actions, and the factors involved in the regulation of the synthesis and secretion of hPL. This review will focus on the role of hPL in the mother and fetus during pregnancy, emphasizing evidence that strongly suggests a role for hPL as a maternal and fetal “growth hormone.” Consideration will also be given to recent studies indicating a role for several novel factors in the regulation of the synthesis and release of hPL. © 1991 by The Endocrine Society.