Understanding The Menstrual Cycle
Updated: Jan 18
Gues blog by Dr Jolene Brighten
Periods... the menstrual cycle.... talking about these can be a taboo. Sure, we might learn the basics in science, but that’s it. Unfortunately, this leads to many women and people who menstruate, young and old, not fully understanding their cycle. This can have a negative effect, as understanding your cycle properly can help you to take your health and happiness into your own hands.
Dr Brighten has produced a simple infographic to help you understand your menstrual cycle better. The original post that went with the graphic can be found here.
The Menstrual Cycle
The menstrual cycle begins from around the age of 10 upwards. On average, periods start at 12 years old. This cycle continues up until around the age of 50, when the menopause usually begins.
The length of the menstrual cycle varies for each individual, but the average is said to be 28 days. However, anything from 21 to 40 days is normal. The cycle is measured from the first day of a period to the day before the next period.
There are two main hormones connected with the menstrual cycle. These are oestrogen and progesterone. Both of these hormones have different roles during your cycle.
In a body that menstruates, oestrogen is mainly produced in the ovaries, but some is also produced by the adrenal glands and fat tissue. It is mainly responsible for the maturation process when children develop into menstruating adults. This hormone is responsible for the growth of breasts and pubic hair. It is also responsible for the beginning of the menstrual cycle.
Progesterone is also produced in the ovaries and the adrenal glands during your cycle (it is also produced by the placenta during pregnancy). This is known as a more “calming” hormone and counters the effects of oestrogen.
Stages Of The Menstrual Cycle
Understanding your menstrual cycle can help with health and wellbeing. It helps you to be “in tune” to your body. There are two ways of looking at the menstrual cycle, these are the ovarian cycle and the uterine cycle. The ovarian cycle describes the changes within the follicles of the ovary, whereas the uterine cycle describes the changes to the lining of the uterus.
The Ovarian cycle includes the Follicular Phase, Ovulation, and the Luteal Phase. Menstruation, the Proliferative Phase, and the Secretory Phase are part of the uterine cycle. Some of these different phases overlap.
We’ve made this simple graphic to make it easy to understand.
Uterine Cycle - Stage 1 – Menstruation
The Menstruation Phase begins on the first day of your period and ends when you finish bleeding. This is the first stage of your menstrual cycle.
During this stage, your uterus sheds its lining. Both hormones (Oestrogen and Progesterone) are found in low levels during this phase.
Ovarian Cycle – Stage 1 – Follicular Phase
The Follicular Phase of the Ovarian Cycle overlaps two parts of the Uterine Cycle – Menstruation and the Proliferative Phase.
On the first day of Menstruation, the low levels of Oestrogen and Progesterone cause the pituitary gland (found in the brain) to release Follicle-Stimulating Hormone (FHS). This hormone stimulates the ovaries to form a follicle in preparation for ovulation.
Uterine Cycle – Stage 2 – Proliferative Phase
This part of the Uterine Cycle occurs whilst the Ovarian Cycle Follicular Phase is still happening. As the follicles mature, they secrete increasing amounts of oestrogen. This causes the lining of the uterus to build up as the uterus prepares to release an egg and possible pregnancy.
Ovarian Cycle – Stage 2 – Ovulation
This stage of the Ovarian Cycle happens when a mature follicle releases an egg. During ovulation, the follicle produces more oestrogen to prepare for pregnancy. Depending on your cycle, at around 12-14 days the oestrogen levels reach their peak and cause Luteinising Hormone (LH) to be released. This surge in LH causes ovulation.
After being released, the egg travels down the fallopian tube. If it is fertilised the egg implants into the lining of the uterus. If fertilisation does not occur, the egg is dissolved and passed out of the body during menstruation.
Uterine Cycle – Stage 3 – Secretory Phase
This is the last stage of the Uterine Cycle and marries up with the Luteal Phase of the Ovarian Cycle. The Secretory Phase happens straight after ovulation.
During the Secretory Phase, the corpus luteum in the ovary (this is the ruptured follicle that released the egg) produces progesterone. This phase is important in making the uterus ready for implantation by an embryo.
Ovarian Cycle – Stage 3 – Luteal Phase
As the Secretory Phase of the Uterine Cycle causes an increase of progesterone, the Luteal Phase in the Ovarian Cycle also occurs. FSH and LH levels cause the remaining ruptured follicle to transform into the corpus luteum.
The increased progesterone causes the production of oestrogen to also increase. During the latter part of this phase, as the corpus luteum is broken down, progesterone begins to decrease (if the egg has not been fertilised). These falling levels of progesterone trigger menstruation and the beginning of the next cycle.
Understanding your menstrual cycle can help you to understand to ebb and flow of your hormones and how they affect your body and mood. This can help you prepare for each phase of your cycle and manage your periods.
Dr Brighten is a leader in female health who is passionate about helping people to understand their cycles, which empowers them to take control of their hormones and health. You can find more about her work on her website.