Uterine Cycle
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Uterine Cycle

July 13, 2021


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Did you know your uterine cycle and your menstrual cycle are the same things? You can use the terms interchangeably, though some people mistakenly think that the menstrual cycle refers only to menstruation (or active bleeding). For this reason, we find that we can improve clarity by using the term “uterine cycle,” which refers to the various phases our female bodies go through every month.


Though we may be tempted to silently (or loudly) curse our uterine cycles when we’re going through menstruation, if we really think about what’s going on inside our bodies, we should be super impressed. Every month, our hormones do a beautiful dance that allows the endometrial lining to prepare for pregnancy. If no pregnancy happens, our bodies automatically know what to do to prepare for the next cycle. There’s some amazing choreography that’s happening right now inside your uterus, without your input or direction.


What Is the Uterine Cycle?

The uterine cycle is a simple term that refers to the complicated hormone and physiological changes the uterus and other reproductive organs go through during a typical menstrual cycle. These changes affect the lining of the uterus (also known as the endometrium) and involve ever-changing hormone levels (primarily estrogen and progesterone, though luteinizing hormone, estradiol, and oestrogen/estrogen are also involved). There are some abnormal and normal menstrual cycle characteristics to watch out for each month.


As estrogen and progesterone levels increase and decrease, the hormone changes can lead to various physiological and emotional fluctuations. That’s why you may feel extremely energetic during one phase of your cycle, then want to veg all day in bed during another phase. You can thank estrogen and progesterone for changes in your food cravings each month, as well.


What Are the Phases of the Uterine Cycle?

The uterine cycle has four main phases: Menstruation, the follicular phase, the ovulatory phase, and the luteal phase. Estrogen, progesterone, and other hormones are in constant flux throughout these phases. Let’s talk about each of these phases of the cycle in greater detail and how they affect your endometrium.


Phase 1: Menstruation


Here’s a brief period overview in case you forgot what happens to your body during menstruation. Menses is the phase of the uterine cycle that tends to get the most attention. It’s when your uterine lining (also known as your endometrium) sheds because it’s no longer needed (no implantation of an egg). Menstruation is triggered by a drop in the hormones estrogen, estradiol, and progesterone. Later in the cycle, estrogen, estradiol, and progesterone will increase.


Some women experience heavy menstrual flow during this phase, while others experience mild menstrual bleeding. The severity of bleeding often depends partially on balance between the hormones progesterone and estrogen in the body. Some women may experience missed or irregular periods due to physiological issues such as polycystic ovarian syndrome.


Menstrual bleeding may last anywhere between two to seven days for most women. However, some women may experience bleeding or spotting for up to two weeks every menstrual cycle. Abnormally long periods could be an indication of a problem, so it’s wise to get checked out if your menstrual periods are consistently longer than ten days.


Phase 2: The Follicular Phase


The follicular or proliferative phase of your uterine cycle is when your uterine lining regenerates. This happens once your body is finished with the menstrual bleeding phase and estrogen levels rise. Throughout this phase, the endometrial thickness increases until ovulation occurs. Your body also increases its production of cervical mucus. The purpose of the proliferative phase is to prepare your body once again to nurture a fertilized egg. A human egg needs certain conditions to thrive and grow, and the proliferative phase of your menstrual cycle helps prepare the ideal environment for pregnancy to occur.


During the follicular phase, your anterior pituitary gland releases follicle stimulating hormone (FSH). FSH leads to the development of primordial follicle groups. FSH also stimulates the growth of eggs. As your ovarian follicles mature, most of them die off to make way for secondary follicles surrounded by supporting granulosa cells.


Eventually, a Graafian follicle emerges. This is a mature ovarian follicle that releases an egg into the fallopian tube during ovulation. When the egg is released, it’s referred to as follicle rupture. Though it sounds painful, many women don’t feel it happen. Others may feel some discomfort when the primary follicle grows and ruptures. This is often referred to as ovulation pain.


Phase 3: The Ovulatory Phase


Ovulation is when the dominant follicle releases a mature egg into the fallopian tube. This important part of the ovarian cycle puts the egg in a prime position to be fertilized by incoming sperm. A fertilized ovum can then go on to develop into a fetus. Ovulation is the only phase of the menstrual cycle during which pregnancy can occur. That’s why it’s so important to understand the symptoms of ovulation if you’re trying to get pregnant.


On the flip side, it’s also important to recognize when ovulation occurs in your body if you want to avoid getting pregnant. It’s wise to avoid intercourse during ovulation if you’re not ready to become a parent. Ovulation typically lasts anywhere between 12-24 hours. However, you should also know that sperm tend to be rugged little guys that can live in your body for up to five days. Keep that in mind when planning your lovemaking sessions.


Some of the most common indications of ovulation include cervical mucus that is thinner, clearer, and more slippery than usual and a resting (or basal) temperature that falls a little bit before rising again. Your most fertile time is two to three days before your temperature rises.  


Estrogen peaks just before ovulation then drops afterward. Ovulation is marked by an increase in luteinizing hormone (also known as LH). An LH surge triggers ovulation. Once the luteinizing hormone increases, it only takes up to two days for the mature egg to be funneled into the fallopian tube. If it isn’t soon penetrated by sperm, it will die.


Phase 4: The Luteal Phase


Once the ovulatory phase ends, the luteal phase begins. It’s also commonly referred to as the secretory phase of the menstrual cycle. The secretory phase is when the uterine glands and arteries supplying your reproductive tissues regenerate. It’s also the time when your body helps form the corpus luteum. The corpus luteum was once the dominant follicle but now begins to produce both progesterone and estrogen.


The secretory phase of the menstrual cycle is usually around 13 days long. However, this timeline can vary from person to person. If there is no fertilized ovum to nurture at the end of the secretory phase, your body will move right along to the menstrual phase again. During the luteal phase, progesterone rises, peaks, then drops off.


How Long Does the Uterine Cycle Last?


A regular menstrual cycle lasts an average of 28 days for most women. However, it may be shorter or longer for some people. In the typical female of reproductive age, the entire cycle may be anywhere between 21 and 35 days. Progesterone and estrogen levels can help determine the length of your cycle.


Get Your Cycle Under Control


Minor variances in the menstrual cycle are normal, but wild variances aren’t. Let’s work together to get our hormones under control so our bodies function the way they were intended to. Hertime supplementation is a tasty and effective way to start.

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