Ovaries: function, hormones and what you can measure

Your ovaries are two almond-shaped organs of about 3 centimetres each, sitting left and right of your uterus. They do two jobs at once: they store your entire supply of eggs and they produce the hormones that run your cycle, your skin, your bones and your energy.

For organs that manage this much, you hear remarkably little about them. Until something plays up.

So in this piece: how your ovaries work, what you might feel, and which blood values tell you something about them.

What is the function of the ovaries?

Your ovaries have two tasks. One: deliver a mature egg each cycle for a possible pregnancy. Two: produce the hormones oestrogen and progesterone, plus a small amount of testosterone. Together they drive your menstrual cycle and reach every corner of your body.

The supply of egg cells you're born with is stored in thousands of small sacs, the follicles. Each month a group of them starts maturing, and usually one wins and ovulates.

At 30, about 12 percent of your original reserve remains; at 40, around 3 percent (PMID 20111701). The process continues until menopause, when the supply has nearly run out.

Which hormones do your ovaries make?

Your ovaries produce three types of hormones themselves, and respond to two signalling hormones from your brain. The useful part if you like to know where you stand: each of these hormones has a measurable blood value. The table below links every hormone to its role and to what can be measured.

If you'd like several of these values measured at once, the fertility assessment bundles them into a single draw.

What do you feel when your ovaries are bothering you?

Usually a one-sided, nagging or stabbing pain low in your abdomen, left or right of the middle. A short twinge around ovulation is completely normal; it's called ovulation pain and passes on its own. Pain that lasts for days, keeps returning or comes with a bloated belly deserves a GP appointment.

A common and usually harmless cause is an ovarian cyst: a fluid-filled sac that often disappears by itself.

Mind one exception. Sudden, severe one-sided pain, sometimes with nausea, can point to a twisted ovary. That is an emergency: call your GP or the out-of-hours service straight away.

What are the symptoms of inflamed ovaries?

An inflammation of the ovaries and fallopian tubes (PID) often causes lower abdominal pain, pain during sex, unusual discharge and sometimes fever. Symptoms can also stay mild and vague, which is why the condition is easily missed. Dutch GP guidance (Thuisarts) advises seeing your doctor with these symptoms, because an untreated infection can damage the tubes.

The cause is usually an ascending infection, for example chlamydia or gonorrhoea.

This is emphatically not a DIY diagnosis: hormone blood tests say nothing about it. These symptoms belong with a GP, not a webshop, ours included.

Ovaries and PCOS

With PCOS, the ovaries hold many small follicles at the same time. That picture often comes with an irregular cycle, acne or excess hair growth, and with an AMH value two to three times higher than average. Since the 2023 international guideline, that AMH measurement may even replace the ultrasound in diagnosing adults (PMID 37580037).

If this pattern sounds familiar, read our article on PCOS testing.

What does blood testing say about your ovaries?

Blood testing answers two questions reasonably well: roughly how large your egg reserve still is, and whether your hormone production fits your cycle phase. The reserve question is AMH territory; the production question belongs to oestradiol, progesterone, FSH and LH together.

What blood doesn't see: cysts, a torsion or an infection. That's what ultrasound is for.

Take Sanne, 33, whose cycle hasn't returned after stopping the pill. An AMH of 5.8 micrograms per litre next to a shifted FSH/LH ratio fits PCOS, while an AMH of 0.4 sets up a very different GP conversation. Same complaint, different direction.

So my advice is simple: use blood values to sharpen your conversation with your GP, never to skip it.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP or your gynaecologist.

References

• Wallace WH, Kelsey TW. Human ovarian reserve from conception to the menopause. PLoS One, 2010. PMID 20111701.
• Teede HJ, Tay CT, Laven JJE, et al. Recommendations from the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. Hum Reprod, 2023. PMID 37580037.
• La Marca A, Spada E, Grisendi V, et al. Normal serum anti-Müllerian hormone levels in the general female population. Eur J Obstet Gynecol Reprod Biol, 2012. PMID 22579227.
• Thuisarts.nl. Ik heb een ontsteking aan mijn eileiders en eierstokken.