When it comes to managing menstrual cycles, many women, and individuals with a female reproductive anatomy try not to think about it and simply power through ‘the period’ as a regular thing… it’s predictable, it’s annoying, and we want it to end as fast as possible!  More often than not, we don’t have a full understanding about how our hormones influence our menstrual cycle and how hormones can change as we age. Hormone levels in our body evolve over time, starting at puberty when our period first begins, to menopause when a full year has passed with no more menstrual periods. If it sounds like an easy ride, think again – many people have experienced a kind of ‘hormonal gymnastics’ during every decade (and sometimes every month) of their lives.

Don’t worry though because healthyher.life is here with our new info-series Hormones 101, which will help explain the fundamentals of hormone health and answer those questions you’ve always wanted to ask but were afraid to. So, whether you are experiencing problems with your menstrual flow, dealing with unbearable pelvic pain, planning to get pregnant, or wondering if you’re in perimenopause, we have it covered… keep reading below😊.

​

What type of reproductive hormones do I have? [1], [2]

Women and individuals with female reproductive anatomy have a set of hormones that play a crucial role in regulating menstrual cycles and the activity of the reproductive organs - these are:

• Follicle-Stimulating Hormone (FSH) – stimulates the follicles, which are the fluid-filled sacs in the ovaries that contain egg cells (a.k.a. ovum, plural ova), to produce estrogen and get the body ready to release an egg during ovulation.

• Luteinizing Hormone (LH) – produced by the pituitary gland in the brain, LH triggers the body to ovulate (i.e., release an egg, or ovum) during your menstrual cycle.  LH also helps to create a temporary and normal cyst inside the ovary after the egg has been released, which is called the corpus luteum, and also promote the release of progesterone hormone.

• Estrogens – includes a group of natural steroid hormones released by the ovaries to help the egg  mature in the ovary prior to its release. The major sources of estrogen in the body are the ovaries and the placenta (the temporary pregnancy organ that nourishes the fetus and remove waste), while much smaller amounts are secreted by the adrenal glands, as well as the male testes.

• Progesterone – a female steroid sex hormone that is released from the corpus luteum and helps with thickening of the uterine lining during the luteal phase of your cycle (more about this explained below). The thickened endometrium (or wall lining) prepares the uterus for implantation of a fertilized egg.

• Testosterone – the hormone responsible for maintaining general body health and sexual desire. Most of the testosterone that is made in women and individuals with a female reproductive anatomy gets converted by the body into estrogen and helps the body release an egg during ovulation.

How are my hormones involved in the menstrual cycle? [3]

​Whether you are just starting to learn about your menstrual cycle, or you’ve weathered the monthly menstrual storm for a few decades, everyone should know that the average menstrual cycle for a female lasts 28 days.

The diagram in Figure 1 illustrates a normal 28-day menstrual cycle in which the levels of reproductive hormones FSH (Follicle Stimulating Hormone), LH (Luteinizing Hormone), Estrogen and Progesterone will change during each of the 3 menstrual cycle phases: 

Follicular Phase → Ovulation → Luteal Phase

​Below we will explain what happens to your body during each of the three phases.

Figure 1. Hormone changes during the average 28-day menstrual cycle without a fertilization event. FSH is Follicle Stimulating Hormone and LH is Luteinizing Hormone. Shaded gray area is the Ovulation phase, which represents when you are most fertile.

Follicular Phase - Days 1 to 13 of your cycle

Days 1-7: Menstruation

The Follicular Phase begins on Day 1 with the start of menstruation (the first day of your period) where your body is shedding the cellular lining of your uterus, which is blood. During this menstruation period that lasts an average of about 5-7 days (however it can be a longer or shorter period), you may experience symptoms such as uterine cramps, bloating of your abdomen and some weight gain, tender breasts, mood swings, and irritability. Your estrogen levels are generally low during the first 7 days of the Follicular Phase. [3, 4]

Days 8-11: Production of egg cells

Immediately following the end of menstruation, your estrogen levels will start to increase as your body prepares for ovulation (the release of ova, or egg cells). The FSH and LH hormones are also increasing during this phase to stimulate the ovaries to produce egg cells. By the end of this period, the FSH hormone level decreases slightly so that only one of the egg cells continues to grow and mature.

​Days 11-15: Fertility Window

Days 11 to 15 following the start of your menstruation (which is Day 1 of your cycle) is the period leading up to ovulation, or the release of a mature egg cell (ovum) and is considered the “fertility window”.  During this short period of approximately 4-5 days, females will have a higher chance of becoming pregnant than any other time during your entire menstrual cycle.

​Ovulation: Day 14

Your body’s FSH and LH hormones are at peak level by Day 14, which causes the ovaries to release a mature egg. You are most fertile around Day 14, which is the Ovulation phase. The LH hormone, which triggers the body to ovulate (i.e., release the egg), also helps create a temporary and completely normal cyst of cells called the corpus luteum inside the ovary after the egg (ovum) has been released. [3, 4]

​

Luteal phase:  Day 15 to 28  

​Days 15-24

Following ovulation and the release of an ovum, your body’s FSH and LH levels decrease substantially, and the corpus luteum begins to release progesterone hormone (Figure 1). Progesterone and estrogen work together to thicken the lining of the uterine wall (called the endometrium), to allow a fertilized egg to implant itself. [1, 4, 5]

Days 25-28

All hormone levels begin to drop, and if the egg (ovum) is not fertilized by sperm, the corpus luteum will break down and shed itself along with the cells of the uterine lining, which appears as menstrual bleeding and the start of a new menstrual cycle.

 It is during the latter part of the Luteal Phase that you are likely to experience the symptoms of Premenstrual Syndrome (PMS) like bloating, weight gain, headaches, and mood changes. Some people may also experience Premenstrual Dysphoric Disorder (PMDD) which is a severe form of PMS.

​

What happens if I become pregnant?

​If the ovum released during ovulation (around Day 14 of your cycle) becomes fertilized by a sperm cell, the fertilized egg will implant itself in the thickened uterine wall (endometrium). The diagram in Figure 2 shows the changes in hormone levels during a cycle of 28-day if there is fertilization of the released egg.  The implanted and fertilized egg will develop into an embryo, triggering the production of a hormone called human Chorionic Gonadotropin (hCG) (see Figure 2). The hCG hormone helps to maintain progesterone production by the corpus luteum in order to support the growth of the embryo.  At this stage, estrogen levels are also high to ensure the uterine lining (endometrium) stays thick throughout the pregnancy to support the embryo, and eventually the unborn fetus. [3, 6]

Figure 2. Hormone changes during a cycle of 28 days that includes a fertilization event (if you become pregnant), which is marked with a star.

​

​What happens if I take oral contraceptives (e.g., birth control pills)?

​Oral contraceptives (defined as pharmaceutical medications that counteract or prevent conception, or fertilization of the egg) have the function to prevent pregnancy by stopping ovulation and the maturation of egg cells (ova). Contraceptive medications will have a progesterone-like hormone component that diminishes the body’s production of FSH and LH, which reduces a female’s ability to ovulate. Many types of contraceptive medications also have a synthetic estrogen-like hormone component.  [7]  The menstrual period that happens while you are taking oral contraceptives such as birth control pills is called withdrawal bleeding, and it takes place during the 7 days when you take the placebo pills (the sugar pills that have no hormones), as a result of the change in your body’s hormones levels.

Now that you understand the physiology basics of how your reproductive hormones work to bring about your menstrual cycle, we will next explain what is going on in your body when you have a dysregulated hormonal health, such as the perimenopause and menopause transitions, or when your hormonal health might be abnormal and lead to serious and debilitating conditions like endometriosis and polycystic ovarian syndrome (PCOS).