The 4 hormones running your entire month, explained simply
You've probably heard the words estrogen and progesterone. Maybe you've noticed them mentioned when someone talks about mood swings, cramps, or the pill. But do you know what they actually do — not just in broad strokes, but day by day across your cycle? And what about FSH and LH — the two hormones that most people have never heard of, but without which none of the others would work at all?
Your menstrual cycle is orchestrated by four hormones working in a precise relay — each one rising or falling at a specific moment, triggering the next in sequence, and shaping everything from your energy and mood to your skin, sleep, and appetite. Understanding them is one of the most useful things you can do for yourself. Because once you know what each hormone does and when it peaks, the way you feel at different points in your month stops being mysterious and starts making complete sense.
Meet the four hormones
Where it comes from
FSH is produced by the pituitary gland — a small gland at the base of your brain that acts as the body's hormonal control center. It is released in response to signals from the hypothalamus, the brain region that oversees the entire hormonal relay.1
What it does
FSH starts each new cycle. Rising in the days after your period begins, FSH travels through the bloodstream to your ovaries and stimulates a group of follicles — small fluid-filled sacs, each containing an immature egg — to begin growing and maturing. As they grow, the follicles produce estrogen, which rises steadily through the first half of the cycle. Only one follicle will become dominant and go on to release an egg.2
When it peaks
FSH is highest in the early follicular phase — the first week or so after menstruation begins — and drops once estrogen is high enough to signal back to the pituitary that the follicles are developing well.
How you feel when it's working
Where it comes from
Estrogen is produced primarily by the growing ovarian follicles during the first half of the cycle, and in smaller amounts by the corpus luteum and adrenal glands.3 There are three forms — estradiol, estrone, and estriol — with estradiol being the most active during the reproductive years.
What it does
Estrogen is the cycle's most wide-reaching hormone. It rebuilds the uterine lining after menstruation, supports brain function by boosting serotonin and dopamine, improves sleep quality, sharpens cognitive function, increases social confidence, and supports bone density, skin health, and cardiovascular function.4 When estrogen is rising, most women feel noticeably more energized, clear-headed, and emotionally resilient. When it drops sharply — as it does before the period — the withdrawal is felt across the entire body and brain.
When it peaks
Estrogen reaches its highest point just before ovulation — triggering the LH surge that causes the egg to be released. It rises again briefly in the mid-luteal phase before falling sharply in the days before menstruation.
How you feel when it's high
Where it comes from
Like FSH, LH is produced by the pituitary gland in response to signals from the hypothalamus. The two hormones work closely together throughout the cycle, but LH has one specific and critical moment: the surge.5
What it does
LH's primary role is to trigger ovulation. When estrogen reaches a critical peak mid-cycle, it sends a positive feedback signal to the hypothalamus — causing a sharp, dramatic surge in LH release. This LH surge — typically lasting 24 to 36 hours — signals the dominant follicle to rupture and release its egg into the fallopian tube.2 After ovulation, LH also stimulates the empty follicle to transform into the corpus luteum, which then produces progesterone for the remainder of the cycle.
When it peaks
The LH surge occurs approximately 24 to 36 hours before ovulation — usually around day 12 to 14 of a 28-day cycle, though this varies significantly between women and between cycles.6
How you feel when it surges
Where it comes from
After ovulation, the empty follicle transforms into a temporary structure called the corpus luteum. The corpus luteum is the primary producer of progesterone in the second half of the cycle. If pregnancy doesn't occur, the corpus luteum breaks down after 10–14 days — and progesterone falls with it.3
What it does
Progesterone prepares the uterine lining for a potential pregnancy — thickening it, increasing its blood supply, and making it receptive to implantation. It also raises basal body temperature, slows gut motility, has a calming (sometimes sedating) effect on the brain via GABA receptors, and suppresses further FSH and LH release.7 When progesterone is stable in the early luteal phase, many women feel settled and calm. But when it drops sharply in the late luteal phase, the GABA support it provided withdraws — and irritability, anxiety, poor sleep, and emotional sensitivity often follow.
When it peaks
Progesterone rises steadily after ovulation, peaks around day 21 of a 28-day cycle, and then falls sharply if pregnancy hasn't occurred. This fall triggers the shedding of the uterine lining — your period.
How you feel as it rises and falls
How the four hormones work together — the relay
The four hormones don't just act independently. They communicate with each other and with the brain in a continuous feedback loop — each one influencing the next in a precise sequence that repeats every cycle.2
FSH rises → follicles develop → estrogen climbs
The cycle begins when FSH rises after menstruation. FSH stimulates follicle growth. Growing follicles produce estrogen. Estrogen rises steadily through the follicular phase, building the uterine lining and lifting mood and energy.
Estrogen peaks → LH surges → ovulation
When estrogen reaches a critical threshold, it triggers a positive feedback signal to the brain — causing the LH surge. The LH surge signals the dominant follicle to rupture and release its egg. This is ovulation — typically around day 14.
LH surge → corpus luteum forms → progesterone rises
After releasing its egg, the empty follicle transforms into the corpus luteum under LH's ongoing influence. The corpus luteum produces progesterone, which rises through the luteal phase — preparing the uterine lining for potential implantation.
No pregnancy → corpus luteum breaks down → all hormones fall → period begins
If no egg is fertilized, the corpus luteum degenerates after 10–14 days. Progesterone and estrogen both fall sharply. This drop signals the uterus to shed its lining — menstruation begins — and FSH starts to rise again, beginning the next cycle.7
Quick reference — all four hormones at a glance
| Hormone | Produced by | Main role | Peaks when | You feel |
|---|---|---|---|---|
| FSH | Pituitary gland | Stimulates follicle growth | Early follicular | Energy slowly returning |
| Estrogen | Ovarian follicles | Mood, energy, cognition, uterine lining | Just before ovulation | Sharp, confident, energized |
| LH | Pituitary gland | Triggers ovulation | Mid-cycle surge | Peak drive and confidence |
| Progesterone | Corpus luteum | Prepares uterus, raises temperature | Mid-luteal phase | Calm early, emotional late |
Why knowing this changes everything
Most women go through their entire reproductive lives experiencing the effects of these four hormones without ever understanding what's driving them. The energy crash, the mood lift, the irritability, the brain fog, the confidence, the exhaustion — all of it has a hormonal author. And knowing which hormone is responsible for what you're feeling at any given point in your cycle changes the experience fundamentally.
It replaces confusion with pattern. Self-blame with biology. And the feeling that your body is unpredictable with the understanding that it is, in fact, running a remarkably precise and repeating sequence — one that you can learn to read, anticipate, and work with rather than against.
You now know the four hormones. Feelings shows you which part of the relay your body is running today — with expressive mood avatars that reflect how each phase actually feels.
References
- NIH — StatPearls. (2023). Physiology, follicle stimulating hormone. NCBI Bookshelf
- Reed, B.G. & Carr, B.R. (2018). The normal menstrual cycle and the control of ovulation. Endotext, NCBI. NCBI
- NIH — StatPearls. (2023). Physiology, progesterone. NCBI Bookshelf
- Barth, C., Villringer, A., & Sacher, J. (2015). Sex hormones affect neurotransmitters and shape the adult female brain. Frontiers in Neuroscience. PubMed
- NIH — StatPearls. (2022). Physiology, luteinizing hormone. NCBI Bookshelf
- Barbieri, R.L. (2014). The endocrinology of the menstrual cycle. Methods in Molecular Biology / PubMed. PubMed
- NIH — StatPearls. (2024). Physiology, menstrual cycle. NCBI Bookshelf
- Cleveland Clinic. (2025). Follicle-stimulating hormone (FSH): what it is and function. Cleveland Clinic