• Megan Gross

Your Hormones 101 - Progesterone

Your Hormones 101 – Progesterone


Progesterone. We’ve all heard of it. But do you know where it comes from? Or what it does in your body? Today I’m going to explain all of that and more!



Progesterone is a steroid hormone that is almost exclusively created from the corpus luteum. Now what is the corpus luteum you ask? It is a structure left behind after a follicle is released during ovulation. The corpus luteum houses the maturing follicle until it is released, and then it sits on the ovary and releases progesterone until it degrades completely and menstruation occurs. It usually lasts for 12-16 days, but generally around 14 days. If pregnancy occurs, then at that time the developing placenta will take over for progesterone production. If pregnancy doesn’t occur, the decrease in progesterone from the disintegrating corpus luteum will cause menstruation to occur.


Progesterone, though she may not stick around for very long, has a whole host of functions throughout the body. First and foremost, the goal of progesterone is to help sustain a pregnancy should conception occur after ovulation. This starts with helping to guide sperm to the ovum. Next it will slightly decrease your immune system response, so that if implantation occurs, the body will not reject the developing embryo. Have you noticed you’re more susceptible to illness after ovulation? You’re not going crazy, there’s a biological reason for this!


Progesterone also decreases the contractility of your uterus as well as all of your smooth muscles. Though you may not realize it, your uterus regularly contracts. Progesterone slows down these contractions so that if there is a fertilized ovum, it won’t be expelled. You may also notice during the second half of your menstrual cycle that you experience more feelings of constipation. The colon is made up of smooth muscle, and it is impacted by increased levels of systemic progesterone.


My favorite function of progesterone is its effect on the brain. Progesterone causes a sense of overall calm on the brain directed towards potential brain inflammation, which helps to reduce anxiety. Progesterone has been used exogenously to help with traumatic brain injury as its calming effect helps with brain healing. Women experiencing a deficiency of progesterone are at a higher risk for experiencing depression and anxiety.


Progesterone also plays a role in various other functions in the body including developing breast tissue during puberty, affecting libido, and decreasing breast milk production. We know that majority of women’s progesterone comes from the corpus luteum, but there is a small amount that doesn’t, this means that men can also have measurable amounts of progesterone in their bodies, which if too high, can negatively impact their libido. As always when hormones are at play, it is a delicate dance to ensure that everything remains in perfect harmony.

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