Periods & cycle

Estrogen, Progesterone, LH, FSH: Your Cycle's Hormones

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The menstrual cycle is run by four hormones: FSH and estrogen dominate the follicular first half, a mid-cycle LH surge triggers ovulation, and progesterone leads the luteal second half before a drop starts your period. According to ACOG, typical cycles last 21 to 35 days [1].

Last updated: July 2026

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Which four hormones run your menstrual cycle?

Four hormones do most of the work in a typical cycle: estrogen, progesterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH). According to the American College of Obstetricians and Gynecologists, the menstrual cycle is a vital sign, averaging 21 to 35 days in adults and 21 to 45 days in the first few years after a first period 1.

FSH and LH are released by the pituitary gland in the brain, while estrogen and progesterone are made mainly by the ovaries 2. Each one rises and falls on a schedule rather than staying flat, which is why your energy, ovulation signs, and flow can shift across a single month.

How does the feedback loop keep the cycle on schedule?

A feedback loop between the hypothalamus, pituitary gland, and ovaries keeps the four hormones in sequence. The hypothalamus releases gonadotropin-releasing hormone, which prompts the pituitary to send out FSH and LH; these in turn tell the ovaries how much estrogen and progesterone to make 2.

Rising estrogen early in the cycle first suppresses FSH, then flips to trigger the sharp LH surge that releases an egg around cycle day 14 of an average 28-day cycle 3. According to the Endocrine Society, disruptions to this loop from low energy, high stress, or intense training can stall ovulation 2. FSH also climbs naturally as ovarian reserve declines with age, part of the shift into perimenopause 4.

What does each hormone do across the two phases?

Each hormone peaks in a different window, splitting the cycle into two halves. In the follicular phase, FSH recruits a batch of follicles and estrogen climbs to thicken the uterine lining and produce fertile cervical mucus 3.

After the LH surge and ovulation, the emptied follicle becomes the corpus luteum and releases progesterone for roughly 12 to 14 days, steadying the lining and raising basal body temperature by about half a degree Fahrenheit 1. If no pregnancy occurs, progesterone falls, the lining sheds, and bleeding begins, closing one loop and opening the next. A first-half estrogen lead and a second-half progesterone lead is the core pattern of every cycle.

How do these hormones shape the symptoms you feel?

Symptom patterns track the hormone curve more than the calendar. Rising estrogen in the follicular phase often lifts energy and mood, while the post-ovulation progesterone rise can bring bloating, breast tenderness, and sleepiness in the luteal week 5.

The premenstrual drop in both hormones is linked to the mood and physical symptoms many people notice in the days before bleeding; the Cleveland Clinic notes that a smaller group has the more severe pattern of premenstrual dysphoric disorder 5. When ovulation does not happen, estrogen can act without a progesterone counterbalance, a common reason for irregular periods and heavier bleeding 6. Cycle-to-cycle variation of a few days is normal.

When cycle hormone patterns need a clinician

Most cycle-hormone shifts are normal, but a few patterns are worth a professional review. Cycles shorter than 21 days or longer than 35 days, bleeding that soaks through protection hourly, no period for 90 days, or severe premenstrual mood symptoms are all reasons to check in with a clinician 16.

A primary care clinician or gynecologist can order hormone testing, review your tracking, and separate a benign fluctuation from a condition like thyroid disease or PCOS. According to the Office on Women's Health, keeping a simple cycle log makes these visits more productive 3. Gale can help you prepare for that conversation.

Common questions

The luteinizing hormone (LH) surge is the direct trigger. Rising estrogen late in the follicular phase flips from suppressing to stimulating the pituitary, producing a sharp LH spike that releases the egg within about a day and a half. FSH rises alongside it but plays a smaller role in the release itself.

Some can be estimated at home. Ovulation predictor kits detect the LH surge in urine, and basal body temperature tracking reflects the progesterone rise after ovulation. Blood tests ordered by a clinician measure estrogen, progesterone, FSH, and LH more precisely, and timing matters because each hormone is only meaningful on certain cycle days.

Cycle hormones are not identical every month. Sleep, stress, illness, travel, and changes in exercise or eating can all shift the size and timing of the estrogen and progesterone peaks, so premenstrual symptoms may feel stronger in some cycles. A pattern of steadily worsening symptoms is worth discussing with a clinician.

Yes. Combined hormonal contraception supplies steady synthetic estrogen and progestin that suppress the natural FSH and LH surges, which is how they prevent ovulation. The monthly bleed on the pill is a withdrawal bleed when the hormones pause, not the same event as a natural period driven by your own ovaries.

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When cycle changes deserve a check-in

  • —Cycles regularly shorter than 21 days or longer than 35 days - track them and raise it with a clinician
  • —Bleeding heavy enough to soak a pad or tampon every hour for several hours - contact a clinician promptly
  • —No period for 90 days when you are not pregnant - schedule an evaluation
  • —Severe premenstrual mood symptoms that disrupt work or relationships - ask a clinician about PMDD

This article is general health education, not medical advice. Whether your cycle hormones are behaving normally depends on your full history and is best interpreted with a primary care clinician or gynecologist.

References

  1. 1.American College of Obstetricians and Gynecologists (2015). ACOG Committee Opinion No. 651: Menstruation in Girls and Adolescents: Using the Menstrual Cycle as a Vital Sign. Obstetrics & Gynecology. doi:10.1097/AOG.0000000000001215 ✓Normal menstrual cycle parameters and cycle length (21-35 days in adults, 21-45 days in early adolescence); the menstrual cycle as a clinical vital sign
  2. 2.Gordon CM, et al. (Endocrine Society) (2017). Functional Hypothalamic Amenorrhea: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism. doi:10.1210/jc.2017-00131 ✓The hypothalamic-pituitary-ovarian axis, GnRH/FSH/LH signaling, and how disrupted signals from low energy availability, stress, or intense training can stall ovulation
  3. 3.Office on Women's Health (U.S. HHS) (2025). Period problems. Office on Women's Health (womenshealth.gov), U.S. HHS. link ✓Basic menstrual cycle physiology, ovulation timing, and the estrogen-then-progesterone sequence across the follicular and luteal phases
  4. 4.Harlow SD, Gass M, Hall JE, et al. / STRAW+10 Collaborative Group (2012). Executive summary of the Stages of Reproductive Aging Workshop +10: addressing the unfinished agenda of staging reproductive aging. Menopause. doi:10.1097/gme.0b013e31824d8f40 ✓Rising FSH as ovarian reserve declines with reproductive aging and the transition toward perimenopause
  5. 5.Cleveland Clinic (2023). Premenstrual Dysphoric Disorder (PMDD). Cleveland Clinic (tier-2). link ✓Luteal-phase hormone shifts, premenstrual symptoms, and premenstrual dysphoric disorder as a more severe pattern
  6. 6.American College of Obstetricians and Gynecologists (2013). ACOG committee opinion no. 557: Management of acute abnormal uterine bleeding in nonpregnant reproductive-aged women. Obstetrics & Gynecology. doi:10.1097/01.AOG.0000428646.67925.9a ✓Anovulatory bleeding from unopposed estrogen without a progesterone counterbalance as a cause of irregular and heavy bleeding

6 sources, numbered by first appearance. General health information, not medical advice. AI-assisted editorial content — every citation independently verified. Editorial policy

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