The two primary female sex hormones are estrogen and progesterone. Both are produced mainly by the ovaries and together control menstruation, pregnancy, and a wide range of functions throughout the body. But several other hormones play essential supporting roles in female reproductive health, from the signals that start puberty to the hormones that make breastfeeding possible.
Estrogen and Its Three Forms
Estrogen is the hormone most associated with female biology. It drives the development of breasts, hips, and other physical changes during puberty, regulates the menstrual cycle, and helps maintain bone density, skin elasticity, and cardiovascular health. What many people don’t realize is that “estrogen” is actually a group of three related hormones, each dominant at a different life stage.
Estradiol is the strongest and most abundant form from puberty through menopause. It fluctuates throughout the menstrual cycle, peaking just before ovulation. Estrone is a weaker form that becomes the primary estrogen after menopause, when the ovaries slow their production. Estriol is the weakest of the three and rises dramatically during pregnancy, when it becomes the dominant form.
Progesterone
Progesterone works alongside estrogen but has a distinct job: preparing the body for pregnancy each month. After ovulation, the empty follicle in the ovary transforms into a temporary structure called the corpus luteum, which pumps out progesterone. This hormone thickens the uterine lining so a fertilized egg can implant. If pregnancy doesn’t occur, progesterone levels drop, the lining sheds, and a period begins.
During pregnancy, progesterone production shifts to the placenta and remains elevated for months, helping sustain the pregnancy and preventing the uterus from contracting too early. Outside of reproduction, progesterone also influences mood, sleep quality, and body temperature, which is why some people notice feeling warmer or sleeping differently in the second half of their cycle.
FSH and LH: The Brain Hormones That Run the Cycle
Estrogen and progesterone don’t act on their own. They take orders from two hormones released by the pituitary gland, a small structure at the base of the brain: follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
FSH does what its name suggests. In the first days of each menstrual cycle, it stimulates the growth of about 15 to 20 follicles in the ovaries, each containing an egg. As these follicles grow, they begin producing estrogen. Rising estrogen eventually signals the brain to cut back on FSH, so only one dominant follicle continues developing.
LH then takes over. A sudden surge of LH around the middle of the cycle triggers ovulation, causing the dominant follicle to release its egg. LH also stimulates the corpus luteum to produce progesterone in the second half of the cycle. Both FSH and LH are themselves triggered by a hormone from the hypothalamus called gonadotropin-releasing hormone (GnRH), making the whole system a chain of signals from brain to ovary and back again.
Testosterone in Women
Testosterone is typically labeled a “male” hormone, but women produce it too, in smaller amounts, primarily in the ovaries and adrenal glands. Its exact role in female health isn’t completely understood, but it contributes to sexual desire, arousal, and the maturation of vulvar and vaginal tissues. It also appears to influence energy levels and muscle maintenance. Testosterone levels in women decline gradually with age, particularly after menopause.
Hormones of Pregnancy and Breastfeeding
Pregnancy introduces a few hormones that are either absent or barely detectable at other times. Human chorionic gonadotropin (hCG) is the hormone detected by pregnancy tests. It’s produced by the developing placenta and helps maintain progesterone production in early pregnancy before the placenta can take over that job on its own.
Oxytocin, sometimes called the “love hormone,” plays a central role in childbirth. It drives the powerful uterine contractions that dilate the cervix, move the baby through the birth canal, and push out the placenta. After delivery, oxytocin continues working by triggering the release of breast milk during nursing. It also promotes feelings of bonding and nurturing between parent and baby.
Prolactin is the hormone directly responsible for breast milk production. Levels rise during and after labor, preparing the body for breastfeeding. High prolactin during early breastfeeding may also support a woman’s emotional adjustment to motherhood and help foster caretaking behaviors. Endorphins, the body’s natural pain-relieving hormones, also surge during labor and can create a sense of alertness or even euphoria after birth, which may help strengthen the early bond with the newborn.
How These Hormones Change Over a Lifetime
Female hormone levels are not static. They shift dramatically across major life stages, and those shifts explain many of the physical and emotional changes women experience.
At puberty, the hypothalamus begins releasing GnRH in a pulsing pattern for the first time, which kicks off FSH and LH production and starts the ovaries producing estrogen. This rising estrogen is what triggers breast development, the widening of hips, and eventually the first menstrual period.
During the reproductive years, estrogen and progesterone cycle roughly every 28 days. Estradiol levels can swing from around 20 pg/mL at the start of a cycle to as high as 750 pg/mL at the midcycle peak, then drop again before a period. These fluctuations are behind many familiar cycle-related symptoms like bloating, breast tenderness, and mood shifts.
Perimenopause typically begins eight to ten years before menopause, as the ovaries gradually produce less estrogen. Cycles may become irregular, and symptoms like hot flashes and sleep disruption often start during this phase. By menopause, the ovaries have largely stopped releasing eggs and no longer produce significant amounts of estrogen or progesterone. Estradiol levels drop to 20 pg/mL or below, and estrone becomes the body’s primary (though much weaker) estrogen.
How Female Hormones Work Inside Cells
Estrogen and progesterone are steroid hormones, meaning they’re built from cholesterol and are small enough to pass directly through cell membranes. Once inside a cell, they bind to specific receptor proteins. Before a hormone arrives, these receptors sit inactive, bundled up with helper proteins. When the hormone attaches, the receptor releases those helper proteins, changes shape, and moves to the cell’s DNA. There, it acts like a switch, turning certain genes on or off. This is why hormonal changes can affect so many different tissues at once: any cell with the right receptor can respond, whether it’s in the uterus, brain, bones, or skin.