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An Introduction to the Menstrual Cycle

An Introduction to the Menstrual Cycle
An Introduction to the Menstrual Cycle

How much do you know about your menstrual cycle?

Most of the answers I get are pretty much similar to: "I bleed once a month".

This is a great and valid answer, however, it shows how many of us really know what's going on with our monthly cycle. Now, there’s certainly no shame in not knowing the details, but how would you feel about knowing some of the basics?

Let me explain the fundamentals.

Menstrual cycle basics

Your menstrual cycle is governed and controlled by a set of different organs that are in constant communication. This communication system is called the Hypothalamus-Pituitary-Ovarian axis (HPO-axis). The hypothalamus communicates with the pituitary gland and the pituitary gland communicates with the ovaries and vice versa. The communication happens via hormones that are produced in the glands and transported from one to another via the blood.

The main hormones that are involved in regulating your menstrual cycle are (trust me there are more, but let's focus on these ones):

  • GnRH (Gonadotropin-Releasing Hormone)

  • FSH (Follicular Stimulating Hormone

  • LH (luteinizing Hormone)

  • Progesterone

  • Estrogen

GnRH is secreted by the Hypothalamus, FSH and LH are secreted by the pituitary gland and estrogen and progesterone are secreted by the ovaries.

GnRH stimulates the secretion of FSH and LH in the pituitary gland.

FSH stimulates the growth of follicles in the ovaries, before the release of an egg from one follicle during ovulation.

LH is involved in puberty, ovulation, and pregnancy. An "LH surge" triggers ovulation during the cycle

Estrogen is predominantly responsible for the physical changes that turn girls into women: the growth of breasts and pubic hair and the beginning of the menstrual cycle. Your ovaries are the main point of the production of estrogen, with the adrenal glands and fat tissue acting as some secondary points of production. Estrogen moves throughout your body affecting nearly every tissue, including your brain, bones, heart, skin, and more. Estrogen is higher during days 1-14 of your cycle.

Produced mainly in the ovaries and the adrenal glands (and the placenta when pregnant), progesterone is known as the more “calming” hormone of the two. Progesterone “counters” the effects of estrogen in the body, reducing anxiety, increasing sleepiness, helping to build and maintain bone, and promoting appetite and fat storage, among other things. Progesterone ramps up and is higher during days 15-28 of your cycle.

I hope you can follow me up until here!

Four phases of the menstrual cycle

Phase 1 (Menstruation Day 1-5)

The first phase of your menstrual cycle is Menstruation. This is the time when your body eliminates and sheds the lining of your uterus and your period begins.

Phase 2 (Follicular Phase Day 6-11)

On day 1 of your cycle, both estrogen and progesterone are low, which signals the pituitary gland (a pea-sized gland at the base of the brain) to release Follicle-stimulating hormone (FSH). FSH stimulates the ovaries to form a follicle in preparation for ovulation.

Phase 3 (Ovulatory phase Day 12-14)

Ovulation is the part of the cycle where a mature follicle (part of the ovary) discharges an egg. It’s during this time that the egg travels down the fallopian tube and either implants in the endometrium (uterine lining) if fertilized by sperm or slowly dissolved and passed out of the body, along with the uterine lining during your period.

The follicle produces more estrogen to prepare the uterus for pregnancy. For around days 12-14 of the cycle, estrogen peaks and triggers the release of luteinizing hormone (LH). This LH surge causes ovulation.

Phase 4 Luteal phase (15-28)

The ruptured follicle, now called the corpus luteum releases progesterone and estrogen to prepare for pregnancy. If pregnancy occurs, estrogen and progesterone stay high throughout, a phenomenon commonly mimicked with most hormonal birth controls. If pregnancy does not occur, estrogen and progesterone drop, and your period occur.

Phew, that wasn't that bad, was it?

In the next few blogs, I will share more about Cycle Tracking, Hormonal Imbalance, and how to nourish your cycle. Stay tuned!

Xx Mareike

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