Whenever perimenopause is discussed, estrogen is usually the first hormone that people think of, but we tend to forget (or even dismiss) progesterone (pro-gest-er-rone). We know progesterone has a crucial role when it comes to periods so shouldn’t it be an important hormone to consider in perimenopause?
To better understand progesterone, let’s start with discussing how it impacts your cycle. Estrogen is predominant during the first half of your cycle (known as the follicular phase). It helps to regrow the uterine lining (endometrium) that was shed during your period. But it also produces receptors for progesterone, getting the uterus ready for the second half of the cycle (known as the luteal phase).
After ovulation, progesterone becomes the star of the show. Progesterone binds to those receptors on the uterus and thickens the endometrium in preparation for pregnancy. That’s why the origin of the word progesterone has the root of the word “gestation” in it.
One of the crucial changes that can occur during perimenopause is we start ovulating less consistently until we reach menopause, and we stop ovulating all together. What a lot of women don’t realize is if we’re not ovulating, it can dramatically impact progesterone production.
The reason for this is that progesterone is secreted mostly by something called the corpus luteum, which is found in our ovary. The egg that is ovulated comes from the follicle, essentially a multi-celled house surrounding the egg that helps it grow and develop. Once that egg leaves the protection of the follicle, the follicle turns into the corpus luteum. The corpus luteum is what secretes progesterone.
So, as we age, we have less follicles with eggs. The less follicles with eggs we have, the less chance we have to ovulate. If we don’t ovulate, there is no corpus luteum formed. And with no corpus luteum, there is no progesterone being made from the ovary.
The problem this creates in perimenopause is that since we have some months without a large increase in progesterone, estrogen is still present, sometimes in high amounts. This is what is termed “unopposed estrogen” or also known as “estrogen dominance”.
So, in other words, think of progesterone as the yin to estrogen’s yang. Progesterone is the big sister that helps keep estrogen in check. Without progesterone to help mitigate estrogen’s effects, the result can be problematic.
Estrogen dominance has been linked to many health conditions including fibroids, breast cancer, and endometriosis to name a few.
But just like estrogen, progesterone does more than just prep the uterus for pregnancy.
Progesterone has been shown to improve sleep, which is perhaps why insomnia is common in perimenopause. It has also been demonstrated to balance mood and is effective at reducing anxiety. There have even been studies testing progesterone and its ability to reduce seizure activity, due to its calming effect on the brain.
We also know that progesterone increases the production of thyroid hormones as well as improves the sensitivity of receptors to those same hormones. Thyroid health tends to decline as we enter perimenopause. Whether this is exacerbated by or due to declining levels of progesterone is currently unknown but interesting, nonetheless.
There has also been promising research into progesterone’s effect on memory, cognitive diseases like Alzheimer’s, and nerve function so there is much more research that needs to be done.
My suspicion is that progesterone does a whole heck of a lot more than we currently recognize. The majority of research around female hormones focuses solely on estrogen but it stands to reason if estrogen has body-wide effects, why wouldn’t progesterone?
While this all may seem like a moot point since the levels of progesterone and estrogen ultimately decline once we cross the menopause threshold, those levels don’t decline to zero. In fact, it’s more like our ovaries go into retirement than shrivel up and die. (Menopause used to lovingly be referred to as “death of sex”).
And other parts of our body help to pick up the slack, in particular our adrenal glands. An important hormone produced from our adrenals is DHEA, which is the topic of the next article.