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Sinead Brophy Jun 7, 2020 1:00:00 PM 22 min read

Your Cycle, Your Hormones - Your Fifth Vital Sign


Your Fifth Vital Sign

I am not sure about you, but I spent a lot of my life disconnected from my body and my cycle.

I wondered why I felt fatigued at certain times and then was surprised when my period arrived. I got annoyed at myself for being tired or flat and resented my twin brother for not having to deal with a monthly bleed. I didn’t fully understand what hormones were doing what nor did I realise that they could be used to my advantage.


Our cycles are our fifth vital sign. Our bodies like to be in a state of balance and any sense of threat (lack of available food, high levels of stress, health issues, overtraining) can cause our cycles to go out of whack or stop altogether. We often push through the fatigue, think that we should do more, be better, etc. instead of listening to what our bodies are telling us and working with it to get the most out of ourselves, our health, and our training.


JOIN MY WORKSHOP : You can learn to track your cycle to understand your body better, improve performance and adapt your training and nutrition strategies to work with your body, not against it.


Sinead Brophy - Weightlifting - FFS Gyms



Looking at your hormones


We have lots of different hormones circulating around our body, but for women our two main sex hormones are Oestrogen and Progesterone and they are produced by our ovaries.


In our cycles, we also have Gonadotropin Releasing Hormone (GnRH), Lutenising Hormone (LH) and Follicular Stimulating Hormone (FSH). These hormones, released from the hypothalamus and pituitary gland in the brain, work in conjunction with the ovarian hormones; this is known as the Hypothalamic-Pituitary-Ovarian (HPO) axis. It is responsible for the regulation of our menstrual cycle.


Sorry what?

Don’t worry if your head is spinning right now all you need to worry about is that your Menstrual Cycle is linked to the hormonal glands in your brain. This is important because the stress hormone Cortisol, is also linked to these two glands via the Hypothalamic-Pituitary-Adrenal axis (HPA), , and you guessed it, this can have a knock-on-effect on your cycle.


Furthermore, cortisol uses the same building blocks as oestrogen and progesterone and can reduce the body’s ability to produce these hormones.



Stress and Your Cycle - Nicole M Jardim


Source: Dr Nicole M Jardim https://www.instagram.com/nicolemjardim/


Our main sex hormones

Hormones are complex things, but here is a quick overview of our two main sex hormones:



  • Maisie Hill refers to this as your ‘Beyonce’ hormone - it gives you energy, makes you feel sexy and social and helps you to learn new skills.
  • It is anabolic (eg. it helps to grow muscle)
  • It stimulates bone formation
  • It increases tendon and ligament laxity around ovulation (more at risk of ACL and other tendon/ligament injuries)
  • Too little oestrogen can result in menstrual disturbances, loss of period, osteoporosis, heart disease.
  • Too much oestrogen can result in breast tenderness, heavy periods, PMS symptoms, and breast cancer



  • Maisie Hill refers to progesterone as your ‘Kirsten Stewart’ hormone - you can feel a bit anxious, perhaps a bit withdrawn and you want to slow down and relax.
  • It is catabolic (eg. breaks down muscle proteins)
  • Increases our body temperature and breathing rate
  • Helps to stop bone loss
  • Sufficient amounts of progesterone over a long period of time (eg. multiple cycles) is good for your brain health and mood



DID YOU KNOW!? : Covid-19 is having a big impact on women’s menstrual cycles around the world. Dr. Jessica Piasecki in Nottingham Trent University is doing a study on the impact of Covid-19 via FitrWoman. Get involved and further science of female physiology!



FitrWoman - Covid-19 Study

   Source: Fitrwoman https://www.instagram.com/fitrwoman/

Looking at the Menstrual Cycle


There are a number of different cycles that you can have dependent on the type of contraception that you are on


Natural Cycle & Copper Coil

Your menstrual cycle is a ‘monthly cycle’ of hormones that over the course of 28-36 days (this is highly dependent on the individual) stimulate ovulation and grow your uterine lining in preparation for a potential pregnancy (whether we want to get pregnant or not).



Cycle Graphics V2-04


The Follicular Phase (Low Hormone Phase > Ovulation)

  • Day 1 of your cycle begins with the start of your period (first day of bleeding), which can last anywhere between 4-8 days .
  • The pituitary gland in your brain releases Follicle Stimulating Hormone (FSH) and Lutenising Hormone (LH), both of which stimulate the follicles in your ovaries to mature and release an egg during ovulation.
  • As the follicle is maturing it starts to release oestrogen. Oestrogen is the main hormone during the first half of your cycle, the ‘follicular phase’; it along with LH rises just before ovulation and stimulates the ovary to release the egg.
  • We also have some testosterone - important for strength, power, and bone health - which peaks just before ovulation.



The Luteal Phase (Ovulation > Period or Menses)

  •  Once you have ovulated the follicle that once held the released egg now becomes a temporary gland on your ovary called the corpus luteum.
  • Oestrogen drops slightly after ovulation and then it starts to climb again.
  • LH stimulates the corpus luteum to start producing progesterone, which is responsible for supporting the uterine lining in preparation for pregnancy. The luteal phase is normally 14 days long and is known as the ‘high hormone phase’.
  • If no pregnancy has occurred, your progesterone and oestrogen drop. This is normally 3-5 days before your period. This triggers an inflammatory response and the release of prostaglandins which are responsible for the cramps and contractions that result in your period.


DID YOU KNOW!? : You can use the hormones of your natural cycle to improve health and performance!

You can work with your cycle to adapt training and nutrition strategies and harness the power of your hormones….pretty amazing stuff. 


Oral Contraceptive Pill


There are a number of different oral contraceptive pills available but the premise of most pills is that you take a pill with synthetic hormones for three weeks and then have one week where you take a non-hormone pill or no pill at all.


The synthetic hormones stop ovulation (as well as change your cervical mucus) and therefore your bleed on the pill is a withdrawal bleed and not a period.


There is a monophasic type, which is where you take the same dose of hormone(s) for three weeks and then 1 week off. The triphasic pill is where the hormones in the pills change over the course of three weeks to mimic our body’s own rise and fall of hormones. There are also progestin-only pills.


Note: I am not a doctor or a health care provider, so I encourage you to learn more about what pill you are on in your own time.


Learn more :



DID YOU KNOW!? : You can use the hormones of your natural cycle to improve health and performance! Join me this Tuesday at 7pm to learn about how to work with your body not against it.


Losing your period & Menstrual Dysfunction


It is really important that we have periods, losing your period is normally a red flag that something is going on - either overtraining, underfueling, high levels of stress, a combination of these, or something else.


Period Loss

Hypothalamic Amenorrhea (HA) is the loss of your period due to insufficient oestrogen and it can be caused by :


  • Psychological Stress - eg. COVID-19
  • Excessive Exercise
  • Disordered Eating/Insufficient energy intake (aka. Low Energy Availability)


All of the above can have an impact on our stress hormones as well as negatively impacting our Lutenising Hormone (which as you can see from above is really important for producing both oestrogen and progesterone).


This is also known as RED-S (relative energy deficiency in sport), and was formerly known as the Female Athlete Triad.


Health implications of Period Loss or Other Menstrual Dysfunctions


  • Fertility
  • Osteoporosis
  • Cardiovascular disease
  • Mental health
  • Sports performance


If you are experiencing period loss or irregular period, I would strongly recommend speaking to your GP to rule out any underlying conditions and then working with a coach, nutritionist, and/or therapist to


DID YOU KNOW!? : Studies have shown that 45%-65% of of recreational athletes (i.e. you and me) are at risk of low-energy-availability.


So as you can see, our hormones and our cycles are just these things that happen to us. They hold vital clues about our health, both physical and mental, so I would encourage you to learn more about your cycles and how to work with your body, not against it.




JOIN MY WORKSHOP : You can learn to track your cycle to understand your body better, improve performance and adapt your training and nutrition strategies to work with your body, not against it.


Sources & Further Reading:


Follow me on Go with the Flow - Work with your body to learn more about your menstrual cycle and how to work with it, not against it.



  • Roar, Dr. Stacy Sims
  • Fertility Friday & Fifth Vital Sign
  • Period Power, Maisie Hill
  • Period Repair Manual, Lara Briden
  • Just Eat It, Dr Laura Thomas
  • No Period. Now What? Dr. Nicola Rinaldi

Apps & Blogs

  • FitrWoman App Insights
  • Hello Clue Blog
  • Natural Cycles Blog
  • Maisie Hill Blog


Research Papers:

  • Black, Katherine; Slater, Joanne; Brown, Rachel C.; Cooke, Rebecca Low Energy Availability, Plasma Lipids, and Hormonal Profiles of Recreational Athletes, The Journal of Strength & Conditioning Research: October 2018 - Volume 32 - Issue 10 - p 2816-2824
  • Hill, E.E., Zack, E., Battaglini, C. et al. Exercise and circulating Cortisol levels: The intensity threshold effect. J Endocrinol Invest 31, 587–591 (2008). https://doi.org/10.1007/BF03345606
  • Mountjoy M, Sundgot-Borgen J, Burke L, et al. The IOC consensus statement: beyond the Female Athlete Triad—Relative Energy Deficiency in Sport (RED-S)British Journal of Sports Medicine (2014) ;48:491-497.
  • Loucks AB, Thuma JR. Luteinizing hormone pulsatility is disrupted at a threshold of energy availability in regularly menstruating women. J Clin Endocrinol Metab. 2003;88(1):297‐311. doi:10.1210/jc.2002-020369
  • Loucks AB, Verdun M, Heath EM. Low energy availability, not stress of exercise, alters LH pulsatility in exercising women. J Appl Physiol (1985). 1998;84(1):37–46. doi:10.1152/jappl.1998.84.1.37
  • Anne B. Loucks, Bente Kiens & Hattie H. Wright (2011) Energy availability in athletes, Journal of Sports Sciences, 29:sup1, S7-S15, DOI: 10.1080/02640414.2011.588958
  • Shufelt, Chrisandra L. MD, MS, Torbati, Tina, , and Dutra, Erika BA, Hypothalamic Amenorrhea and the Long-Term Health Consequences, Semin Reprod Med. 2017 May; 35(3): 256–262.
  • Vanheest, Jaci L.,et al. Ovarian Suppression Impairs Sport Performance in Junior Elite Female Swimmers, Med Sci Sports Exerc. 2014 Jan
  • Williams, N. I., Mallinson, R. J., & De Souza, M. J. (2019). Rationale and study design of an intervention of increased energy intake in women with exercise-associated menstrual disturbances to improve menstrual function and bone health: The REFUEL study. Contemporary Clinical Trials Communications, 14,




Sinead Brophy

Coach Sinead is a certified Personal Trainer, Movement & Mobility Coach, Modern Pregnancy & Postnatal Exercise & Wellness Trainer, and is trained in Female Physiology and Nutrition. Sinead is particularly interested in the female athlete, from how the menstrual cycle impacts training to coaching women in strength and aerobic training during pregnancy. Sinead is leading the way in Dublin in educating women about how to work with their bodies, to harness the power of their hormones, and get the most out of their training. Sinead is heading up Small Group Personal Training for Pregnancy in the new FFS location across the road from the Rotunda, FFS Ivy Exchange Parnell Street - Dublin 1. Email Sinead at sinead@ffs.ie. Find Sinead on Instagram at @sineadbrophy