How Hormones Change During the Menstrual Cycle
Four hormones — FSH, estrogen, LH, and progesterone — rise and fall in a coordinated pattern that drives every stage of your cycle, from your period through ovulation and back again. Here’s what each one does, when it peaks, and how they work together.
The Four Key Hormones
Four hormones drive the cycle: FSH and LH (from the pituitary gland), and estrogen and progesterone (from the ovaries). Each rises and falls at a different point in the cycle, and together they control every phase.
Your menstrual cycle is coordinated by a communication loop between your brain and your ovaries, sometimes called the hypothalamic-pituitary-ovarian (HPO) axis — this axis is the engine behind how hormones change during the menstrual cycle. The hypothalamus releases GnRH in pulses, which signals the pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These, in turn, prompt the ovaries to produce estrogen and progesterone. It’s a feedback loop — rising and falling hormone levels signal back to the brain, which adjusts its own signals in response.
Hormones During the Menstrual Phase
At the start of your period, estrogen and progesterone are both at their lowest point in the cycle. This drop is actually what triggers menstruation — without it, the uterine lining wouldn’t shed. That same shedding process also releases prostaglandins, which is largely why period cramps tend to be strongest in the first day or two. As bleeding begins, FSH starts rising again, signaling the ovaries to begin developing a new group of follicles for the upcoming cycle.
Hormones During the Follicular Phase
FSH stimulates several follicles in the ovaries to develop, each containing an immature egg. Typically one follicle becomes dominant, and as it grows, it produces increasing amounts of estrogen. Rising estrogen does two things: it signals the uterine lining to rebuild after your period, and it eventually triggers the LH surge that leads to ovulation. Interestingly, developing follicles also release a hormone called inhibin, which helps suppress FSH production once a dominant follicle has been established — this is part of why usually only one egg matures per cycle.
The LH Surge and Ovulation
When estrogen reaches a high enough level, it triggers a sharp surge in luteinizing hormone (LH) from the pituitary gland. This LH surge is what actually causes the dominant follicle to rupture and release its egg — ovulation. The surge typically happens 24 to 36 hours before the egg is released, which is exactly what ovulation predictor kits are designed to detect in urine.
Hormones During the Luteal Phase
After ovulation, the ruptured follicle transforms into a temporary hormone-producing structure called the corpus luteum — Its job is to produce progesterone, which rises through the luteal phase to prepare and maintain the uterine lining in case a fertilized egg needs to implant. Estrogen also has a smaller second rise during this phase, though progesterone is the dominant hormone here. If pregnancy doesn’t occur, the corpus luteum breaks down roughly 14 days after ovulation, and both hormones drop sharply — triggering the next period and restarting the cycle.
How Estrogen and Progesterone Work Together
Estrogen and progesterone don’t just rise and fall independently — they regulate each other and the hormones that control them, which is a big part of how hormones change during the menstrual cycle from phase to phase. Rising estrogen in the follicular phase eventually triggers the LH surge (a rare example of estrogen having a positive feedback effect). Once progesterone rises after ovulation, though, it switches to suppressing LH and FSH production, which is part of why you don’t ovulate twice in one cycle. This back-and-forth signaling is also the basis for how hormonal birth control works, since steady synthetic hormone levels prevent the natural surge needed to trigger ovulation.
Hormone Levels Throughout a 28-Day Cycle
Using a 28-day cycle as a general example (Day 1 = first day of your period):
| Cycle Days | Phase | What’s Happening Hormonally |
|---|---|---|
| Days 1–5 | Menstrual | Estrogen and progesterone at their lowest; FSH begins rising |
| Days 1–13 | Follicular | FSH stimulates follicle growth; estrogen rises steadily |
| ~Day 14 | Ovulation | LH surges sharply, triggering egg release |
| Days 15–28 | Luteal | Progesterone rises, then both hormones drop before the next period |
These day numbers are only an example — actual timing shifts with your individual cycle length, since the follicular phase varies more than the luteal phase does.
What Can Cause Hormone Imbalances?
Conditions that can disrupt how hormones change during the menstrual cycle include: PCOS, thyroid disorders, high stress, significant weight changes, over-exercising, and perimenopause. According to Cleveland Clinic, any of these can throw off the normal rise and fall of FSH, LH, estrogen, or progesterone, leading to irregular or late periods, missed ovulation, or unpredictable cycles. Persistent changes are worth discussing with a doctor rather than assuming they’ll resolve on their own.