The ovaries produce three main hormones: estrogen, progesterone, and testosterone. Together, these hormones regulate the menstrual cycle, support pregnancy, influence bone density, and affect everything from mood to muscle mass. The ovaries also produce smaller amounts of lesser-known hormones, including inhibin and activin, that help fine-tune the reproductive system.
Estrogen: Three Forms, Different Life Stages
Estrogen isn’t a single hormone. Your ovaries produce three distinct forms, each dominant at a different point in life. Estradiol is the most potent form and the primary estrogen during your reproductive years. It drives breast development, regulates menstrual cycles, and helps maintain bone strength. Estradiol levels fluctuate significantly throughout a single menstrual cycle, rising as a follicle matures and peaking just before ovulation.
Estriol becomes the dominant form during pregnancy, produced in large quantities by the placenta rather than the ovaries alone. After menopause, the ovaries produce very little estrogen, and estrone becomes the primary form circulating in the body, mostly converted from other hormones in fat tissue and the adrenal glands.
Beyond reproduction, estrogen protects cardiovascular health, supports skin elasticity, and influences cholesterol levels. It also plays a role in brain function, which is one reason some women experience mood changes or cognitive shifts during menopause when estrogen production drops sharply.
Progesterone and the Corpus Luteum
Progesterone’s main job is preparing and maintaining the uterine lining for a potential pregnancy. After ovulation, the empty follicle that released the egg transforms into a temporary structure called the corpus luteum. This structure becomes a small hormone factory, pumping out progesterone during the second half of the menstrual cycle.
If sperm fertilizes the egg, the corpus luteum continues producing progesterone for about 12 weeks, until the placenta takes over. If fertilization doesn’t happen, the corpus luteum breaks down roughly 10 days after ovulation. The resulting drop in progesterone triggers the shedding of the uterine lining, which is what causes your period.
Progesterone also has calming effects on the brain, which partly explains why some women feel more anxious or restless in the days just before their period, when progesterone levels fall steeply. During pregnancy, both the ovaries and the placenta produce progesterone to keep the uterine lining thick, support fetal development, and suppress contractions until labor.
Testosterone in Women
Most people associate testosterone with men, but the ovaries are a meaningful source of this hormone in women too. About 33% of circulating testosterone in women of reproductive age comes directly from specialized cells in the ovaries called theca cells. The rest is produced by the adrenal glands or converted from another androgen, androstenedione, in tissues like fat and skin.
Testosterone in women supports libido, contributes to muscle and bone maintenance, and plays a role in energy levels. It’s also essential for making estrogen. Inside the ovary, theca cells produce testosterone and another androgen, which are then handed off to neighboring granulosa cells. Those granulosa cells convert the androgens into estrogen using an enzyme called aromatase. Without testosterone as a raw material, the ovaries couldn’t produce estrogen at all.
When ovarian testosterone production is too high, it can lead to symptoms like acne, excess hair growth, and irregular periods, a pattern commonly seen in polycystic ovary syndrome (PCOS). Too little testosterone, which sometimes happens after menopause or surgical removal of the ovaries, can contribute to low energy and reduced sex drive.
How the Brain Controls Ovarian Hormones
The ovaries don’t operate independently. They respond to signals from the brain in a tightly coordinated feedback loop. The hypothalamus releases a signaling hormone that tells the pituitary gland to produce two key messengers: follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
FSH acts on the granulosa cells of the ovarian follicles, stimulating them to produce aromatase, the enzyme that converts androgens into estrogen. As estrogen levels rise, they signal back to the brain to adjust FSH output. Meanwhile, LH acts on theca cells, driving them to produce the androgens that granulosa cells need as building blocks. This cooperative process between two cell types responding to two brain hormones is sometimes called the “two-cell, two-gonadotropin” model.
At mid-cycle, a surge of LH triggers ovulation. The entire system relies on constant feedback: hormones from the ovaries tell the brain how much stimulation is needed, and the brain adjusts accordingly.
Inhibin and Activin
The ovaries also produce inhibin and activin, two protein hormones that act as fine-tuning controls for the reproductive system. Inhibin, produced by the granulosa cells, puts the brakes on FSH secretion from the pituitary gland. This helps prevent too many follicles from developing at once. Activin does the opposite, enhancing FSH release. The balance between these two hormones helps ensure that typically just one follicle matures and ovulates each cycle.
Beyond fertility, activin also influences red blood cell production in bone marrow. Both hormones participate in broader biological processes throughout the body, but their primary role relevant to ovarian function is keeping the brain-ovary communication loop precise.
What Changes After Menopause
After menopause, the ovaries dramatically reduce their production of estrogen and progesterone. The adrenal glands become almost the exclusive source of circulating estradiol, estrone, and progesterone. But the ovaries don’t go completely silent.
Postmenopausal ovaries remain responsible for roughly 50% of circulating testosterone and about 30% of androstenedione. This is why surgical removal of both ovaries, even after menopause, can cause a noticeable drop in energy and libido that goes beyond what natural menopause produces. The ovaries may stop being estrogen factories, but they continue contributing meaningfully to androgen levels for years afterward.
How Pregnancy Shifts Hormone Production
During pregnancy, the ovaries share hormone duties with a new organ: the placenta. Early in pregnancy, the corpus luteum in the ovary is the primary source of progesterone, which is critical for maintaining the uterine lining and preventing miscarriage. By around 12 weeks, the placenta has developed enough to take over progesterone production entirely.
The placenta also produces massive amounts of estrogen (primarily estriol), human chorionic gonadotropin (hCG, the hormone detected by pregnancy tests), and human placental lactogen, which helps direct nutrients to the fetus and prepares the breasts for milk production. The ovaries essentially step back as the placenta becomes the dominant hormone-producing organ for the remainder of pregnancy.