Overview of a Women’s Menstrual Cycle

A women’s menstrual cycle (MC) is very individualist: menarche will occur at different ages, we can experience a variety of symptoms, have different cycle lengths, begin perimenopause, and reach menopause at different ages. Therefore, please remember when reading this post to keep an open mind. If your MC is completely different to what I describe that does not make your MC ‘bad’ or ‘unhealthy’, it just makes it different and that is ok.

Overview of the Menstrual Cycle:

The MC generally begins when a girl is around twelve to thirteen years old (when menarche occurs in puberty), but this does differ from person to person as menarche can occur as early as eight or as late as 16 years old (Carmichael et al., 2021, NHS, 2021). From menarche a women’s MC should hopefully be a regular cycle until she reaches perimenopause at roughly forty years old (but we know there are a number of factors which can affect the regularity of a women’s MC – I will discuss in a later post). Typically, one MC lasts between 21 – 35 days, with the average being 28 days (Carmichael et al., 2021). A women’s MC begins when their period begins (first occurrence of a bleed) and ends when the next period commences as this is when the next MC begins.

The MC comprises of two distinct phases: the follicular phase, which is the first phase of the MC, and the luteal phase, the second phase of the MC. Each of these phases can be divided into sub – phases (Figure 1) and are associated with very distinct concentrations of hormones, namely estrogen and progesterone (Pereira et al., 2020).

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Figure 1: Hormonal events and phases of an average 28 day menstrual cycle. Cited from Carmichael et al., 2021.

As demonstrated in Figure 1 during the early follicular phase of our MC hormone levels are quite low and steady, as we enter the later stages of the follicular phase (just before ovulation) our estrogen levels increase. When we reach ovulation, which is approximately around day 14 of our MC, estrogen levels begin to decrease. Whilst our estrogen levels continue to decrease into the luteal phase of the MC our progesterone levels begin to rise; with both hormones levelling off again at the end of one MC. These changes in hormone levels are crucial to understanding our MCs and why we feel the way we do at certain times of our cycle.


I want to point out that I am not yet a registered associated nutritionist or a medical professional by any means so if you do have any concerns/ medical queries speak to your GP in the first instance. I have made a list of some key terms I used throughout this post (in bold) below so please check them out if you are unsure of any terminology.

I hope you’ve found this post interesting, if you did please support my blog by giving this post a like below, it would mean so much 🙂 Also, let me know in the comments below what you thought of this post, what else you’d like to see me research and write about, I would love to chat!

Love, Mais x

Instagram: @wellnesswithmais


Key Terms:

Menarche – The first occurrence of menstruation (aka a women’s period).

Perimenopause – Is a phase, usually several years, of a women’s life before menopause occurs. The ovaries begin to release less estrogen during this phase, the length of a women’s MC will change (this will be a persistent change), thus periods will become less frequent. The most common symptom of perimenopause is irregular menstruation. Women usually enter perimenopause between the ages of forty to fifty, however in some cases you may be younger.

Menopause – A women’s period ceases and it is the end of their MCs.

Estrogen and Progesterone – Two key sex hormones produced by a women’s gonads (the ovaries) which have an array of functions within the female human body, namely the development of female sex characteristics, such as breasts and reproductive organs as well as preparing the uterus for menstruation (Fuentes and Silveyra, 2019) .


References:

CARMICHAEL, M. A., THOMSON, R. L., MORAN, L. J. & WYCHERLEY, T. P. 2021. The impact of menstrual cycle phase on athletes’ performance: a narrative review. International Journal of Environmental Research and Public Health, 18, 1-24.

FUENTES, N. & SILVEYRA, P. 2019. Chapter Three – Estrogen receptor signalling mechanisms. In: DONEV, R. (ed.) Advances in Protein Chemistry and Structural Biology. Academic Press.

NHS. 2021. Starting your Periods [Online]. Available: https://www.nhs.uk/conditions/periods/starting-periods/ [Accessed 23/04/21].

PEREIRA, H. M., LARSON, R. D. & BEMBEN, D. A. 2020. Menstrual Cycle Effects on Exercise-Induced Fatigability. Frontiers in Physiology, 11.

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