Menstrual Cycle 101

Quick Facts

• Your menstrual cycle includes every day between periods, not just bleeding days
• It’s regulated by brain-ovary-uterus signalling, involving oestrogen, progesterone, FSH and LH.
• The cycle has two coordinated systems: the ovarian cycle (egg development) and the uterine cycle (lining preparation).
• Regular ovulation is a key marker of hormonal and metabolic health
• Changes in your cycle can reflect stress, inflammation, nutrient status, thyroid function, or insulin balance.

The menstrual cycle: more than just your period

When people talk about the menstrual cycle, periods tend to take centre stage.

But bleeding is just one outcome of a much larger monthly process.

Your menstrual cycle influences how your body:

• produces energy
• manages stress
• regulates mood
• clears hormones
• supports long-term reproductive and metabolic health

Because of this, medical bodies now recognise the menstrual cycle as a vital sign -offering insight similar to blood pressure or heart rate.

What is the menstrual cycle?

The menstrual cycle begins on the first day of bleeding and ends the day before the next period starts.

It’s governed by two overlapping systems:

• The ovarian cycle: Controls egg development and ovulation.
• The uterine cycle: Controls the build-up and shedding of the uterine lining.

Both cycles are synchronised by hormonal signals from the brain.

The ovarian cycle explained

Follicular Phase (Day 1 → Ovulation)

This phase begins on the first day of your period.

What’s happening:

• The brain releases FSH, stimulating ovarian follicles
• One follicle becomes dominant and prepares an egg
• Oestrogen rises steadily

How you might feel:

More focused, motivated, social, and mentally clear as oestrogen increases.

Ovulation (Mid-cycle)

Ovulation occurs when a surge in LH triggers the release of a mature egg.

Key points:

• Ovulation happens 10–16 days before your next period, not always day 14
• This is your fertile window, lasting around 5–6 days
• Testosterone and oestrogen peak, often supporting confidence and libido

Ovulation is also a sign that the brain–ovary axis is functioning well.

Luteal Phase (Ovulation → Next Period)

After ovulation, progesterone becomes the dominant hormone.

What’s happening:

• Progesterone stabilises the uterine lining
• The body prepares for potential pregnancy
• If pregnancy doesn’t occur, progesterone and oestrogen fall

How you might feel:

Calm and grounded initially, followed by lower energy or mood changes as hormones decline.

This is the phase where PMS or PMDD symptoms may emerge if progesterone is low or inflammation is present.

The uterine cycle explained

Menstrual Phase

Shedding of the uterine lining when hormone levels fall.

Average blood loss is around 60 ml. Very heavy bleeding is worth investigating.

Proliferative Phase

Rising oestrogen rebuilds the uterine lining after menstruation.

Secretory Phase

Progesterone prepares the lining for implantation.
If implantation doesn’t occur, hormone levels fall and the cycle resets.

What’s considered a “normal” cycle?

Typical patterns include:

• Cycle length: 21–35 days
• Period length: 2–7 days
• Ovulation occurring most cycles

Consistency over time matters more than hitting exact numbers.

When cycle changes matter

Cycle disruption can reflect:

• chronic stress or overtraining
• insulin resistance
• thyroid dysfunction
• nutrient depletion (iron, B12, folate)
• conditions such as PCOS or endometriosis

Irregular, absent, painful, or emotionally disruptive cycles are signals, not inconveniences.

Why tracking your cycle matters

Tracking allows you to:

• spot early hormonal shifts
• time blood testing accurately
• understand symptom patterns
• advocate more effectively in healthcare settings

At My Atlas, we often combine cycle tracking with biomarker testing to gain a clearer picture of hormonal health.

Final thoughts

Your menstrual cycle is not something to tolerate or ignore.

It’s a monthly insight into how your body is functioning.

Understanding your cycle allows you to move from symptom management to root-cause clarity – and ultimately, better long-term health.