The Menstrual cycle

On the 28th of May we celebrate Menstrual Hygiene Day in order to raise awareness about menstruation and the importance of good menstrual hygiene management. In honor of this special day, we dedicate the whole month of May to this important topic, one that occurs naturally in half of the global population.

This week, we will be talking about the menstrual cycle, a complex and recurrent process that allows women to conceive (become pregnant). Which hormones control the menstrual cycle and why is it called a cycle? Let’s find out!

The menstrual cycle represents a series of natural changes in female hormone production that make ovulation (when an egg is released from the ovary) and menstruation (monthly vaginal bleeding due to the uterus shedding part of its inner lining when the egg is not fertilized with sperm) possible. This cycle is possible due to the female reproductive system (a complex multi-organ system that involves the ovaries, the fallopian tubes, the uterus (uterine inner lining and cervix), vagina, hypothalamus (region of the brain responsible for releasing hormones and regulating the body temperature) and pituitary gland (the gland that is responsible for regulating vital body functions and general wellbeing).

Women usually have a long reproductive period of approximately 36 years, as the menstrual cycle begins at puberty (can vary from 10 to 16 years of age) and ends at menopause (average age of 51). The length of one menstrual cycle can differ but is around 28 days on average, counted from the start of the menstrual period until the start of the next one.

The menstrual cycle is a complex process, controlled and regulated by hormones, mainly by estrogen, progesterone, the stimulating follicle hormone (FSH), luteinizing hormone (LH), and is comprised of 2 phases, the follicular and the luteal phase.

Phase 1. The Follicular phase

  • It represents the first phase of the menstrual cycle, occurring from day 0 - 14 of the menstrual cycle (considering an average duration of 28 days for the whole menstruation cycle)

  • During this phase, the levels of estrogen increase, which stimulates the development of the ovarian follicle (a sac in the ovaries that contains an egg for fertilization) and the growth of endometrial lining inside the uterus

  • In this phase, a suitable environment for the possible incoming sperm is being created, as channels within the cervix begin to appear which will facilitate the entry of sperm cells

  • On the last day of this phase, day 14, ovulation starts; considering a 28 cycle, ovulation happens 14 days before the menstruation

  • During ovulation, high levels of estrogen stimulate the production of the follicle hormone (FSH) and luteinizing hormone (LH). As a result, the mature follicle breaks and releases the egg.

  • Ovulation is a normal process that is represented by the rupture and release of an egg from the ovary into the fallopian tube where it has the potential to become fertilized and develop into a pregnancy

Phase 2. The Luteal phase