Women produce dozens of hormones, but a core group drives the processes most people want to understand: menstrual cycles, fertility, pregnancy, mood, metabolism, and bone health. The major players are estrogen, progesterone, testosterone, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and several others that rise to prominence during pregnancy and breastfeeding. Here’s what each one does and where it comes from.
Estrogen: Three Forms, Three Life Stages
Estrogen isn’t a single hormone. It comes in three forms, and which one dominates depends on where you are in life. Estradiol is the most potent form and the primary estrogen during your reproductive years. It’s produced mainly by the ovaries and influences everything from your menstrual cycle to bone density, skin elasticity, and cholesterol levels. Estradiol levels shift dramatically across a single cycle, ranging from about 20 pg/mL early in the follicular phase to as high as 750 pg/mL around ovulation, then settling between 30 and 450 pg/mL in the luteal phase.
Estriol takes over during pregnancy. The placenta produces it in large quantities, and it helps support uterine blood flow and prepare breast tissue for nursing. After menopause, estrone becomes the dominant form. It’s weaker than estradiol and is produced mainly by fat tissue, which is one reason body composition affects hormonal health after menopause.
Beyond reproduction, estrogen protects your cardiovascular system, helps maintain bone mineral density, and plays a role in brain function and mood regulation. The sharp decline in estradiol during perimenopause is what drives hot flashes, sleep disruption, and the increased risk of osteoporosis that follows.
Progesterone: Preparing for Pregnancy Every Month
Progesterone rises in the second half of your menstrual cycle, after ovulation. It’s produced by a temporary structure called the corpus luteum, which forms from the empty egg follicle once an egg is released. The hormone’s main job is thickening the uterine lining so a fertilized egg can implant and receive nutrients from a rich network of blood vessels.
If pregnancy doesn’t occur, the corpus luteum breaks down, progesterone drops, and the uterine lining sheds as your period. If conception does occur, the corpus luteum keeps producing progesterone until the placenta is mature enough to take over, usually around weeks 8 to 12 of pregnancy. From that point on, progesterone levels stay elevated. High progesterone prevents ovulation during pregnancy, suppresses uterine contractions to reduce the risk of preterm labor, and helps prepare the breasts for milk production. Your adrenal glands also produce small amounts of progesterone throughout life, independent of the menstrual cycle.
Testosterone and Other Androgens
Women produce testosterone too, just in much smaller quantities than men. The ovaries and adrenal glands each contribute roughly equal shares, together accounting for about 40% to 50% of the body’s total testosterone. The rest is converted from other hormones in tissues like fat and skin.
Testosterone supports sex drive, muscle mass, bone strength, and energy levels in women. When levels are too low, you might notice decreased libido, fatigue, or loss of muscle tone. When they’re too high, as in polycystic ovary syndrome (PCOS), the excess can cause acne, excess facial or body hair, and irregular periods.
Another androgen worth knowing about is DHEA-S, produced by the adrenal glands. It serves as a raw material your body converts into both testosterone and estrogen. DHEA-S peaks in your twenties and gradually declines with age, which is one reason hormonal balance shifts over the decades.
FSH and LH: The Hormones That Run Your Cycle
Follicle-stimulating hormone and luteinizing hormone are produced by the pituitary gland in your brain, and they orchestrate the entire menstrual cycle from above. FSH does what its name suggests: it stimulates follicles in the ovaries to grow and mature an egg during the first half of the cycle. As the follicle grows, it releases rising amounts of estradiol.
When estradiol reaches a high enough concentration near the end of the follicular phase, it flips a switch. Instead of suppressing FSH and LH (which it does at lower levels), high estradiol triggers a surge of both hormones from the pituitary. The LH surge is what actually causes ovulation, releasing the mature egg from the follicle. This mid-cycle LH spike is exactly what ovulation predictor kits detect in your urine.
After menopause, FSH levels rise significantly because the ovaries are no longer responding with estrogen. That’s why an elevated FSH level on a blood test is one of the markers used to confirm menopause.
Pregnancy Hormones
Pregnancy introduces hormones that don’t exist at any other time. The most well-known is human chorionic gonadotropin (hCG). After a fertilized egg implants in the uterine wall, the developing placenta releases hCG to signal the mother’s body that pregnancy has begun. It’s detectable in blood about 11 days after conception and in urine shortly after, which is how home pregnancy tests work. One of hCG’s key early roles is telling the ovaries to ramp up estrogen and progesterone production so the pregnancy can sustain itself.
hCG levels rise rapidly in the first trimester and peak around weeks 8 to 11 before declining. That sharp rise is thought to be a major contributor to morning sickness. Meanwhile, progesterone and estrogen continue climbing throughout pregnancy, reaching levels far higher than anything seen in a normal menstrual cycle.
Oxytocin and Prolactin: Labor and Beyond
Oxytocin plays a critical role during labor by driving the rhythmic contractions of the uterus. Working alongside estrogen and a group of compounds called prostaglandins, it also helps soften the cervix in preparation for delivery. But oxytocin’s role extends well beyond the delivery room. Skin-to-skin and eye contact between mother and baby trigger additional oxytocin release, supporting bonding and emotional attachment.
Prolactin is the hormone behind milk production. During pregnancy, high levels of estrogen and progesterone actually block prolactin from initiating lactation. Once the placenta is delivered and those hormone levels plummet, prolactin can finally do its job. Each time a baby breastfeeds, the suckling stimulates more prolactin and oxytocin release, which keeps milk supply going and triggers the “let-down” reflex that moves milk through the breast. This feedback loop is why frequent nursing helps establish and maintain supply in the early weeks.
Anti-Müllerian Hormone and Ovarian Reserve
Anti-Müllerian hormone (AMH) is produced by cells in developing ovarian follicles. It’s become one of the most common blood tests for women exploring fertility because it provides a snapshot of ovarian reserve, meaning how many eggs you have left. Unlike estrogen or progesterone, AMH stays relatively stable throughout the menstrual cycle, which makes it easy to test any time.
Average AMH levels fall between 1.0 and 3.0 ng/mL, but what’s considered normal varies by age. A 25-year-old might have an AMH around 3.0 ng/mL, while a 35-year-old typically measures closer to 1.5 ng/mL. By age 40, levels often drop to around 1.0 ng/mL. Values below 1.0 are considered low, and below 0.4 is severely low. AMH gives information about egg quantity, not quality, so it’s one piece of the fertility picture rather than the whole story.
Cortisol and Stress Response
Cortisol is produced by the adrenal glands and regulates your body’s response to stress, inflammation, blood sugar, and immune function. It follows a daily rhythm, peaking in the early morning to help you wake up and declining throughout the day. While cortisol isn’t unique to women, its interactions with reproductive hormones matter. Chronically elevated cortisol can suppress the pituitary signals that drive ovulation, which is one mechanism through which prolonged stress can cause missed or irregular periods.
Cortisol also influences where your body stores fat. When levels stay high over time, fat tends to accumulate around the midsection rather than the hips and thighs. This shift in fat distribution carries higher metabolic risk and is one reason chronic stress is linked to cardiovascular and metabolic health problems.