Prostaglandins: WTF Are They and How Do They Show Up in Menstruation?

HormonesMenstrual Health
Written By Emma Letki
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If you’ve ever dealt with period cramps, you know they’re no picnic – the kind of pain that ranges from an uncomfortable ache to a full-on, can’t-move cramp. But why exactly do we feel this? It all comes back to prostaglandins, the mysterious little compounds that play a central role in our menstrual cycle. They’re responsible for a lot of what we feel, from cramps to unexpected bathroom trips. So, what are prostaglandins actually doing in our bodies? And why is understanding them key to making sense of our cycles?

Let’s get the basics out of the way with what prostaglandins are.

Prostaglandins are a group of paracrines. Paracrines are like hormones in that they are molecular compounds that move around in fluids, but unlike hormones they don’t travel very far. They are meant to stay in a single organ, but that doesn’t always happen! 

Prostaglandins were named when a bunch of dudes were studying seamen. They thought that prostaglandins were a super special secretion from the prostate gland. They were wrong. Prostaglandins have been found in most human tissue. 

A quick example of what they do:

  • Involved in inflammation process, through pain perception, vessel size, and regulating clotting 

  • Regulates the contraction of smooth muscle (the muscles in our organs)

  • Helps our endocrine system to create hormones

  • Works with our immune system to produce fever, and regulate white blood cell creation

  • Increase our allergy response

  • Protects our gut by lowering stomach acid secretion while also increasing stomach mucus. 

  • Helps to regulate the production of bone

  • A pivotal part of the menstrual process

This list goes ON, there are tomes written on these guys. BUUUUUTTTT, I want to focus on how it affects menstruating people. 


How Prostaglandins Show Up in Menstruating Bodies

Here is what prostaglandins do in a healthy menstrual cycle!

  1. Before we start bleeding, prostaglandins stop the corpus luteum from  producing progesterone.

  2. Prostaglandins cause vasoconstriction in our endometrium. Limiting the blood supply which helps to break down the endometrium in preparation for shedding. 

  3. Causes muscle contraction in the uterus during menstruation, again helping to shed the endometrium.

  4. Modulate blood flow during menstruation. 

  5. Prostaglandins may have a role  in limiting the number of platelets in menstrual blood (as menstrual blood has fewer platelets in it than normal circulating blood).

  6. The vasoconstriction also helps to stop bleeding after the menstruation phase is over.

Ok, now that the “basics” are over, let’s dive into some more specifics!


Inflammation and Pain:

When our tissues get injured there are a series of steps that happen, these steps are called the inflammation response, an important part of our immune system. Many of the steps are either triggered or supported by prostaglandins. 

Prostaglandins are one of the chemicals that our tissues release to regulate inflammation. They help make our blood vessels more permeable. This is important so that our immune cells (white blood cells) can move out of the blood into the tissue!!!! I think this is so cool! 

Some prostaglandins also help encourage clot formation to seal any damaged tissue. 

Prostaglandins also play a role in pain sensitization. They do this by acting on the nerves surrounding any damaged tissue. To feel something, a nerve has to be activated. To be activated it needs to pass a chemical threshold, then the signal will be sent off to your brain. We have chemicals that lower and raise nerve thresholds (aka make it easier and harder for signals to be sent).  Endorphins raise the threshold making it harder for pain signals to get to the brain (AKA reduce our perception of pain). Prostaglandins lower the nerves threshold, or sensitize the nerve, making it easier for pain signals to get to the brian. 

Sooo, when prostaglandins are around we may feel more pain in that area. 

Let’s link this back to the menstrual cycle.

Right before and during menstruation, our pelvic cavity is flooded with prostaglandins, in our ovaries + corpus luteum, and in our uterus. 

They are present at sites of injury. As much as the menstruation process is normal and healthy, the breakdown of the endometrium and spiral arterioles is a site of injury. So then we get more prostaglandins. 

The inflammation process begins and our bodies regenerate part of our organ! But being flooded with prostaglandins also means that the nerves in the region have been sensitized. This can make shedding the endometrium feel painful (think period cramps, and bloating). 

Unfortunately, higher the amounts of prostaglandins means stronger cramps, and  heightened nerve sensitivity (aka pain).

Another weird but common side effect of prostaglandins floating around our pelvic cavity, is an increased need to defecate. Yup, poop. As we chatted about, prostaglandins make the muscles in our organs contract. And our rectum and lower GI tract have lots of muscles, so we end up pooping a bit more than normal (a lot more in my case!). 

And finally, to add insult to injury, they also play a role in headaches! (But more on that later!)


These guys might seem like sh*t disturbers, but remember they do a lot of good in our bodies too. They are super important in our healing process (AKA the inflammation process). And they are also super important for fertility and pregnancy!

Understanding prostaglandins' roles helps us see that our bodies aren’t betraying us—they’re working hard to support us by coordinating complex actions every month to keep us healthy and balanced. By getting to know what’s happening at a deeper level, we can make choices that support our bodies through each phase of the cycle. Remember, these sensations aren’t just obstacles—they’re part of what makes our bodies so resilient and adaptive.

Have questions about menstruation, cramps, or headaches?

Shoot me an email or book an appointment!

Emma Letki
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