Structural Biochemistry/Human Placental Lactogen


Human placental lactogen (hPL) is a hormone produced exclusively by pregnant women. It is formed in the placenta, which is a tissue that develops during a pregnancy, so non-pregnant women do not produce hPL. The tertiary structure of hPL is similar to that of growth hormone, which all females produce. Like growth hormone, it contributes to the growth of protein tissues. However, hPL is found at exponentially higher concentrations than ugrowth hormone. The highest levels of hPL are observed during the final stages of pregnancy.


Levels of hPL in a pregnant woman can be quantified through a blood test. This information indicates the quality of the functionality of the placenta. If the test shows lower than expected levels of hPL, this suggests toxemia, choriocarcinoma, or placental insufficiency. However, women may also have higher than expected values if they are expecting multiplets, have diabetes, molar pregnancy, or Rh incompatibility.


The main function of hPL is to prevent the movement of glucose into the maternal cells, so that the fetus will be able to accept enough of it to proceed towards normal development. This means an overall increase in glucose levels in the mother's blood stream, although proportionally less glucose is used by the mother's body. Because of this role, hPL contributes to a healthy birth weight of newborns.