In this page we will be talking a lot about the four different phases of the menstrual cycle (if you haven’t read about them – you can read about them in our page “The Four Seasons”), because the hormones, their levels at different times and what they do varies greatly. A hormone is a chemical messenger that tells a part of the body what to do (when to activate, how much of something to produce, etc). Hormones impact many of our body systems and functions such as growth, metabolism, our gastrointestinal tract, emotions, sleep, skin, and energy.During your menstrual cycle, there are four main hormones in play.
There are two hormones produced by the pituitary gland in the brain and released into the bloodstream. These are Follicle stimulating hormone (FSH) and luteinising hormone (LH):
FSH: stimulates the development of the egg in the ovary and the release of oestrogen
LH: stimulates the release of the egg from the ovary (known as ovulation). Also assists in the production of oestrogen and progesterone.
There are two additional hormones produced in the body during the menstrual cycle, but they are produced within the ovaries. These are oestrogen and progesterone. These hormones are more involved in the physical, mental and emotional symptoms you might get during your period.
Oestrogen – This causes growth of the uterine lining which is where an egg will implant or what you will lose during your period. A high amount of oestrogen stops FSH from being produced. Stimulates the release of LH during ovulation (the release of the egg) and then stops the release of LH after the egg has been released. Oestrogen is one of the main female sex hormones. While both women and men produce oestrogen, it plays a bigger role in women’s bodies. It helps during puberty and a level of the hormones which is too low or too high can cause lots of issues in your body.
There are four types of oestrogen produced in the body: Estrone (E1) most prominent estrogen in menopause, Estradiol (E2) most potent and abundant form of estrogen in non-pregnant people in reproductive years, Estriol (E3) created by the placenta in pregnancy, and Estetrol (E4) synthesised by the fetal liver during pregnancy. Estradiol (E2) is the primary cause of symptoms in PMS and surrounding menstruation.
Progesterone – This is the main hormone produced after ovulation, it helps the uterine lining prepare for a pregnancy and it encourages you to slow down in order to prepare your body for a possible pregnancy. It works with oestrogen to stop the production LH after ovulation. If the body becomes pregnant, progesterone is at a high level supporting the body in the early stages and with the development of the foetus. If the body does not become pregnant and a new menstrual cycle begins, caused by extremely low levels of both oestrogen and progesterone.
During this phase of your cycle, you shed your uterine lining (bleeding) and your oestrogen and progesterone levels are at their lowest. This can contribute to general feelings of tiredness and sluggishness, as well as low mood and feeling irritable. Hormones are beginning to rise every day from the first day of your bleed.
FSH and oestrogen are rising in the body, the ovaries are working on developing follicles, the uterus is responding to the oestrogen produced by the follicles, rebuilding the lining that was just shed during the last period.
Oestrogen peaks and causes the production of LH. This causes the dominant follicle to release an egg for potential fertilisation and implantation. Ovulation is a 24 hour event and oestrogen starts to drop afterwards. Progesterone is produced as a byproduct of ovulation when the follicle breaks down into a temporary organ, the corpeus luteum. During this phase, we are at our brightest, most energetic, with lots of motivation to get things done.
This is when the body prepares for a possible pregnancy. FSH, LH and oestrogen are low, but
progesterone is becoming higher. If the egg is fertilised, high progesterone will contribute to maintaining the uterine lining and assisting in the development of the foetus. If the egg is not fertilised, progesterone assists in breaking down the uterine lining and your levels of hormones drop, which might cause PMS if a hormonal imbalance between oestrogen and progesterone is present. This event begins the cycle and the four phases all over again.