The 4 Key Hormones That Run Your Menstrual Cycle

Your menstrual cycle isn’t random — it’s a beautifully coordinated dance between four key hormones so important for fertility:
✨ Oestrogen, Follicle Stimulating Hormone (FSH), ⚡ Luteinising Hormone (LH), and Progesterone.

Each one plays a different role in supporting your fertility, mood, and overall wellbeing.
Here’s a deeper look

Oestrogen (Oestradiol)

Often called the queen of female hormones, oestrogen is produced in the ovaries as follicles develop.
It thickens the uterine lining (endometrium) and supports egg growth.

Levels start low at the beginning of your cycle, rise to a peak just before ovulation, then drop again afterward.
⚖️ Both high and low levels can affect egg quality:

• High oestrogen may indicate PCOS or endometriosis, and can suppress FSH, giving misleading test results.
• Low oestrogen can cause scanty periods, vaginal dryness, or night sweats.

If your body struggles to detox excess oestrogen, you might notice PMS, migraines, fibroids, cramps, or fatigue.
(Castor oil packs can support healthy oestrogen clearance.)

FSH (Follicle-Stimulating Hormone)

Produced by the pituitary gland, FSH stimulates follicle (egg) growth at the start of your cycle.

It’s often used to gauge ovarian reserve — high levels can mean the ovaries are working harder to produce eggs, which may suggest a lower egg supply.

FSH can also rise with adrenal fatigue or hypothyroidism, so it’s worth checking thyroid function too.
Low FSH may appear with amenorrhea, stress, or low body weight — and vitamin C can sometimes support improvement.

FSH is usually tested alongside LH, since the two work in balance and help diagnose issues like PCOS or (rarely) pituitary problems.

⚡ LH (Luteinising Hormone)

Also produced in the pituitary gland, LH helps your follicles make oestrogen early in the cycle.
Then around day 14, LH surges — triggering ovulation and the release of a mature egg.

That surge (about 36 hours before ovulation) is what ovulation predictor kits (OPKs) detect — but remember:
OPKs predict ovulation, they don’t confirm it.

If you have PCOS, your baseline LH can be higher and fluctuate — meaning OPKs may give false positives.
High LH can affect egg quality or cause premature ovulation and early progesterone rise, making the uterine lining less receptive for implantation.

Progesterone

After ovulation, the follicle becomes the corpus luteum, which produces progesterone — the key hormone of your luteal phase.
It calms the nervous system, stabilises mood, and prepares the uterus for a possible pregnancy.

The classic “day 21 progesterone test” actually works best 7 days after ovulation, since not everyone has a 28-day cycle.
Tracking your cycle helps ensure the test is taken at the right time.

Low progesterone can suggest weak ovulation or make it harder for implantation to occur.