HPL* is another of the protein
hormones formed by the placenta. It is similar to the pituitary
HPL can be detected in the
serum at the 6th week of pregnancy, and it's levels continue to
rise with growth of the placenta. In pregnancies with smaller
placentas, there is less HPL detected. The highest concentration
in the blood occurs in late pregnancy.
The functions of HPL are to:
- help prepare the breasts for lactation. It
stimulates breast growth and development and stimulates
the secretion of colostrum.
- to decrease the mother's
use of glucose, so that it can be used by the fetus
for growth and development.
The latter function occurs several ways:
- HPL promotes breakdown of
maternal fats, which results in a higher level of
maternal fatty acids in the plasma. The mother uses the
fatty acids for energy, "saving" the glucose
for the fetus.
- HPL is often
thought of as an "insulin antagonist."
As the level of HPL increases,
it causes an increasing resistance of the
mother's tissue to insulin. Since insulin is
needed to transfer glucose into the mother's
cells, her "resistance" causes the
level of glucose to rise in her blood. HPL
reaches it's peak at about the 23rd week of
pregnancy, when insulin production may not be
able to keep up with the high demands of the
pregnancy. Obviously, the result is a tendency
toward maternal diabetes in pregnancy.
- HPL also affects protein
metabolism, so more amino acids are available for the
fetus. It does this by decreasing the mother's use of
protein for energy and increasing synthesis of protein.
This creates a source of amino acids for transport to the
fetus, resulting in increased levels of protein available
for fetal growth and development.
- Since the mother's tissues are
resistant to insulin, the pancreas is called upon
to secrete additional insulin. This additional
insulin promotes protein synthesis, which again
produces additional amino acids for the fetus.
There will be more information on insulin, the
pancreas, and diabetes later in the course.
*also known as human chorionic somatotropin
Homepage | Course
catalog | Discount
prices | Login | Nursing
jobs | Help