Hormones of the Placenta: Estrogen, Progesterone & hCG

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  • 0:06 Placenta
  • 1:18 Human Chorionic…
  • 1:49 Progesterone and Estrogen
  • 3:35 Human Placental Lactogen (hPL)
  • 4:45 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

The placenta is an endocrine gland that is only present during pregnancy. In this lesson, you will learn about the hormones it produces, including human chorionic gonadotropin (hCG), progesterone, estrogen, and human placental lactogen (hPL).


This might be a peculiar thing to think about, but at certain times in a woman's life, she can create a temporary organ. This organ, that comes and goes, only appears during pregnancy. You may have guessed that the temporary organ I am referring to is called the placenta. In this lesson, you will learn about this remarkable organ and the hormones it produces that help a pregnancy move along smoothly.

The placenta is an organ formed in the uterus of a pregnant woman. The term 'placenta' comes from the Latin language and means flat cake. It may seem strange to think of the placenta in this way, but when we look at a picture of the placenta it does have a flat, roundish shape, similar to a cake.

The placenta transfers nutrients and oxygen to the fetus.
Placenta Diagram

As mentioned earlier, this is a temporary organ. It functions as a connection between the mother and the fetus during fetal development. The placenta is the organ that provides the transfer of oxygen and carbon dioxide, as well as nutrients and wastes, between the mother and the fetus. After delivery, the placenta is expelled from the mother's body as part of the afterbirth, and any hormones that were produced by the placenta fade from the mother's bloodstream.

Human Chorionic Gonadotropin (hCG)

Very early in the pregnancy, we see the production of a hormone called human chorionic gonadotropin (hCG). hCG is actually produced by the fertilized egg after it implants in the uterus and helps maintain the corpus luteum during the early stages of pregnancy. We recall that the corpus luteum is the structure that remains in the ovary after the egg has been discharged. If the egg is unfertilized, the corpus luteum degenerates, and the woman progresses through her normal monthly cycle.

Progesterone and Estrogen

If the egg is fertilized and pregnancy occurs, the corpus luteum is maintained thanks to the hormone hCG. This is important because the corpus luteum produces the hormone progesterone. Sufficient progesterone in a woman's body ensures that the lining of the uterus stays intact and provides a nourishing environment for the egg to implant and develop. Without progesterone from the corpus luteum, the lining of the uterus would slough off, ending the pregnancy.

The corpus luteum, maintained by hCG, produces progesterone.
Corpus Luteum hCG

As mentioned, hCG is produced by the fertilized egg. Therefore, it is the first detectable hormone of a pregnancy and can be detected by blood or urine tests within the first month of conception. For this reason, hCG is the hormone that is tested for when performing a pregnancy test. Regardless of whether a woman purchases a home pregnancy test from her local drug store, or she schedules a more formal test at her doctor's office, the presence of hCG is what denotes a positive test. In the later stages of pregnancy, the job of progesterone production is taken over by the placenta. At that time, the corpus luteum, along with the ovaries, become inactive for the remaining months of the pregnancy.

The placenta also begins producing estrogen. You may recognize estrogen as the hormone that stimulates the development of the female secondary sex characteristics during puberty, such as breast development, hip widening and body hair growth. But, during pregnancy, it serves an additional function, and that is, it helps maintain the pregnancy and prepare the breasts for milk production. The formation and secretion of milk from the mammary glands of a new mother is known as lactation. This milk will be the child's first nourishment after birth if a woman elects to breast feed.

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