Ovaries: definition and meaning
The ovaries are two small, almond-shaped glands that sit on either side of the uterus, near the ends of the fallopian tubes. They have two jobs: storing and releasing eggs, and making the hormones estrogen and progesterone, plus small amounts of testosterone. Together with the brain, they run the menstrual cycle.
What the ovaries do each cycle
- In the follicular phase, FSH from the brain wakes up a group of follicles, each holding an egg.
- One follicle leads and makes more and more estrogen.
- An LH surge triggers ovulation: the follicle releases its egg.
- The empty follicle becomes the corpus luteum and makes progesterone.
- If no pregnancy happens, it fades and a period follows.
The ovaries through life
You are born with all the eggs you'll ever have, around 1 to 2 million. By puberty about 300,000 to 400,000 remain, and only about 400 to 500 are ever ovulated. The number falls steadily, faster after about 35. That remaining supply is called ovarian reserve. When it runs very low, cycles change in perimenopause and eventually stop at menopause.
Common ovary conditions
- Ovarian cysts, usually harmless and temporary
- PCOS, which affects ovulation and hormones
- Premature ovarian insufficiency, when the ovaries stop working normally before 40
- Endometriosis on the ovaries (endometriomas)
- Ovarian cancer, which is rare in younger people
Because the ovaries make the hormones that rise and fall each month, they sit behind many cycle-linked mood changes.
Frequently asked questions
Do the ovaries take turns releasing eggs?
Not strictly. Which ovary ovulates each month is fairly random, though many people notice it alternates.
Can you have periods with one ovary?
Yes. One healthy ovary can usually ovulate every cycle and make enough hormones for regular periods.
What are signs something is wrong with the ovaries?
Persistent bloating, pelvic pain, very irregular or absent periods, or signs like excess hair growth are worth discussing with a doctor.
Sources
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
What is a follicle?An ovarian follicle is a small fluid-filled sac that holds and matures an egg. How follicles grow each cycle, what a dominant follicle is, and why it matters.Ovulation: definition and meaningOvulation is when an ovary releases an egg, usually 12 to 14 days before your next period. Signs, timing, the fertile window, and how it affects mood.
Ovarian cyst: definition and meaningAn ovarian cyst is a fluid-filled sac on or in an ovary. Most are harmless functional cysts that go away. Types, symptoms, and when to seek help.Menstrual cycle hormones: a simple chart of what rises and fallsMenstrual cycle hormones explained simply: how estrogen, progesterone, LH and FSH rise and fall through each phase, and how they shape mood and energy.
Ovarian reserve: definition and meaningOvarian reserve is the number of eggs left in your ovaries. How AMH and follicle counts estimate it, what it can and can't predict, and how age affects it.