Hormones During Your Cycle: Estrogen, Progesterone, LH, FSH

Your menstrual cycle is a hormonal symphony. Four main hormones — estrogen, progesterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) — rise and fall in a carefully coordinated pattern each month. Together, they regulate follicle development, ovulation, uterine preparation, and menstruation. But their effects extend far beyond reproduction: they shape your daily experience of energy, emotion, cognition, and physical comfort.

By understanding when each hormone peaks and drops, you can predict many of the physical and emotional changes you experience throughout the month. This knowledge transforms confusing symptoms into predictable patterns — and empowers you to plan, prepare, and thrive.

How Hormones Drive Your Cycle

The menstrual cycle is governed by a feedback loop between the brain and the ovaries called the hypothalamic-pituitary-ovarian (HPO) axis. The hypothalamus (a brain region) releases gonadotropin-releasing hormone (GnRH), which signals the pituitary gland to produce FSH and LH. These hormones travel through the bloodstream to the ovaries, where they stimulate estrogen and progesterone production. In turn, estrogen and progesterone signal back to the brain, creating a self-regulating feedback system.

This feedback loop is what creates the rhythmic pattern of your cycle. When estrogen is low (during menstruation), the brain ramps up FSH to start growing new follicles. When estrogen reaches a threshold, it triggers the LH surge that causes ovulation. After ovulation, progesterone takes over. When progesterone drops (if no pregnancy occurs), the cycle resets with menstruation.

The precision of this system is remarkable — and understanding it helps you make sense of why you feel different on day 5 versus day 20 of your cycle.

Estrogen: The Energizer

What Estrogen Does

Estrogen (primarily estradiol, or E2) is often called the "feel-good" hormone, and for good reason. Beyond its reproductive role of thickening the uterine lining and supporting follicle maturation, estrogen has widespread effects throughout the body. It boosts serotonin and dopamine production in the brain, enhances verbal memory and cognitive flexibility, promotes collagen synthesis in the skin, strengthens bones, supports cardiovascular health, and increases insulin sensitivity.

When Estrogen Peaks

Estrogen begins rising in the early follicular phase and reaches its primary peak just before ovulation (around days 12–14 in a 28-day cycle). After a brief dip at ovulation, it has a secondary, smaller peak during the mid-luteal phase (around days 21–22) before declining sharply in the late luteal phase, triggering menstruation.

How Estrogen Affects You

Mood and energy: Rising estrogen correlates with increasing energy, optimism, social confidence, and motivation. Many women describe the late follicular phase as when they feel "most like themselves." The estrogen drop in the late luteal phase contributes to the mood decline of PMS.

Skin: Estrogen promotes collagen production, hyaluronic acid synthesis, and healthy skin barrier function. Your skin tends to look its best — clear, hydrated, and glowing — when estrogen peaks around ovulation. The estrogen drop before menstruation can trigger dryness and breakouts.

Cognition: Studies show improved verbal fluency, memory, and creative thinking when estrogen is high. This makes the late follicular phase an excellent time for presentations, exams, writing, and problem-solving.

Physical performance: Estrogen improves muscle recovery, increases pain tolerance, and supports endurance. It also enhances fat metabolism, helping your body use fat as fuel during exercise.

Progesterone: The Calmer

What Progesterone Does

Progesterone is the dominant hormone of the luteal phase. Its primary reproductive function is preparing and maintaining the uterine lining for potential embryo implantation. But progesterone also acts on the brain through its metabolite, allopregnanolone, which enhances GABA receptor activity — the brain's primary calming neurotransmitter system. Progesterone raises basal body temperature, increases breathing rate, has mild sedative properties, and slows gastrointestinal motility.

When Progesterone Peaks

Progesterone is virtually absent during the follicular phase. It begins rising immediately after ovulation (produced by the corpus luteum) and peaks approximately 7 days post-ovulation — around days 21–22 of a 28-day cycle. If pregnancy does not occur, the corpus luteum degrades and progesterone drops sharply over the last few days of the cycle, triggering menstruation.

How Progesterone Affects You

Mood: In the early-to-mid luteal phase, progesterone can create a calm, settled feeling. However, as levels fluctuate and then drop in the late luteal phase, mood instability, irritability, and anxiety can emerge — particularly in women sensitive to allopregnanolone changes.

Energy and sleep: Progesterone's sedative effect means you may feel naturally more tired during the luteal phase. It also disrupts sleep architecture — REM sleep decreases and lighter sleep stages increase, leading to poorer sleep quality even when sleep duration is adequate. This helps explain luteal phase fatigue.

Skin: Progesterone stimulates sebaceous gland activity, increasing oil production. This is why premenstrual breakouts — particularly along the jawline and chin — are so common. The combination of increased sebum and the relative rise in androgens as estrogen drops creates the perfect environment for acne.

Digestion: Progesterone relaxes smooth muscle throughout the body, including the gastrointestinal tract. This slows transit time and can cause constipation, bloating, and gas during the luteal phase. Once progesterone drops and menstruation begins, the opposite effect occurs — prostaglandins speed up motility, sometimes causing diarrhea.

LH: The Ovulation Trigger

What LH Does

Luteinizing hormone is produced by the anterior pituitary gland and plays two critical roles in the menstrual cycle. First, it triggers ovulation: a dramatic surge of LH (increasing 2–6 fold from baseline) causes the dominant follicle to rupture and release the mature egg. Second, after ovulation, LH supports the transformation of the ruptured follicle into the corpus luteum, which produces progesterone.

When LH Peaks

LH remains at low, steady levels throughout most of the cycle. The dramatic LH surge occurs when estrogen from the dominant follicle reaches a critical threshold, approximately 24–36 hours before ovulation. This surge is brief — typically lasting 24–48 hours. This is what ovulation predictor kits (OPKs) detect, making the LH surge the most practical predictor of imminent ovulation.

How LH Affects You

Unlike estrogen and progesterone, LH doesn't have obvious "mood" or "energy" effects that most women notice directly. Its impact is functional — triggering the release of the egg. However, the LH surge often coincides with peak libido, which is likely driven more by the simultaneous estrogen peak and small testosterone spike.

For women tracking fertility, the LH surge is the most actionable signal. A positive OPK (test line as dark as or darker than the control line) indicates that ovulation will likely occur within 12–36 hours. This gives you a clear, time-sensitive window for conception or awareness.

FSH: The Recruiter

What FSH Does

Follicle-stimulating hormone, also produced by the anterior pituitary gland, is responsible for initiating the growth and maturation of ovarian follicles. Each cycle, FSH stimulates a cohort of 5–20 follicles to begin developing. As the follicles grow and produce estrogen, the rising estrogen signals the pituitary to reduce FSH output (negative feedback). This ensures that typically only one follicle — the most estrogen-responsive one — becomes dominant, while the others regress.

When FSH Peaks

FSH rises at the very beginning of the cycle (days 1–4), during what is called the "FSH window." This early rise is what recruits the new cohort of follicles. As estrogen rises from the growing follicles, FSH gradually declines through the mid-follicular phase. There is a small, secondary FSH spike that occurs alongside the LH surge just before ovulation. FSH then remains low throughout the luteal phase.

How FSH Affects You

Like LH, FSH's effects are primarily functional rather than experiential. You don't "feel" FSH the way you feel estrogen or progesterone. However, FSH levels are an important marker of ovarian reserve and reproductive health. Consistently elevated FSH levels (above 10 IU/L on day 3 of the cycle) can indicate diminished ovarian reserve, which is relevant for fertility assessment. FSH levels naturally rise with age as the ovaries require more stimulation to produce follicles.

FSH is also central to fertility treatments — injectable FSH (gonadotropins) is used in IVF and other assisted reproduction protocols to stimulate multiple follicle development simultaneously.

Putting It All Together

Understanding your hormonal cycle is like having a roadmap for the month ahead. Here's a quick summary of the hormonal landscape by phase:

• Menstruation (Days 1–5): All hormones at low levels. FSH begins rising. Energy low, mood neutral to low.
• Follicular (Days 6–13): Estrogen rising, FSH declining. Energy increasing, mood brightening, cognition sharpening.
• Ovulation (Day 14): Estrogen peaks, LH surges, testosterone spikes. Peak energy, confidence, libido, and performance.
• Early Luteal (Days 15–21): Progesterone rising, secondary estrogen rise. Calm, nesting energy, slightly lower drive.
• Late Luteal (Days 22–28): Both hormones dropping. PMS territory — lower mood, fatigue, cravings, sensitivity.

By tracking your cycle and noting your symptoms, mood, and energy each day, you'll begin to see how closely your experience maps to these hormonal patterns. This awareness is transformative — it shifts your relationship with your body from confusion to understanding, from frustration to compassion.