The ovaries are part of a woman’s reproductive system, which is made up of the:
There are 2 ovaries, one on each side of the body. The ovaries produce an egg each month in women of childbearing age.
Women are able to have children between puberty (when the periods start) and the menopause (or change of life, when the periods stop). The age when periods start and stop varies a great deal.
In the middle of each menstrual cycle (mid-way between periods), one of the ovaries releases an egg. It travels down the fallopian tube to the womb. The lining of the womb gets thicker and thicker, ready to receive a fertilized egg. If the egg is not fertilized by sperm, the thickened lining of the womb is shed as a period. Then the whole cycle begins again.
The ovaries also produce the female sex hormones. These are:
The ovaries produce these hormones throughout the years when women can become pregnant. The hormones control the menstrual cycle. As you get older and closer to menopause, the ovaries make less and less of these hormones and periods eventually stop.
More recently doctors have learned that ovarian hormones also help to protect the heart and bones and maintain brain and immune system health.
The ovaries also produce a small amount of the male hormone testosterone. It is not completely clear what role testosterone has in women. But doctors think it helps with muscle and bone strength. And it may have a role in a woman’s sex drive (libido).
In young women the ovaries are about 3cm long. After the menopause they tend to shrink. Doctors can’t usually feel the ovaries during a medical examination, except in young, thin women.
Some women have cysts on their ovaries. Cysts are fluid filled sacks. They are not usually cancerous.
In women of childbearing age, small cysts develop in the ovary every month as an egg develops. This is normal and they usually disappear without treatment within a few months. You should have tests if the cysts:
More than half of ovarian cancer cases are diagnosed in women aged 65 and over.
We don’t know exactly what causes the most common type of ovarian cancer, which is epithelial ovarian cancer. But some factors may increase or reduce the risk.
Factors that may increase the risk include:
Factors that may reduce the risk include:
There are different types of ovarian cancer. The type depends on the type of cell the cancer started in.
Most cases of ovarian cancer are epithelial ovarian cancers. This means the cancer started in the surface layer covering the ovary.
The incidence of ovarian cancer is 3.8-5/100000 in India. This makes ovarian cancer the 5th most common cancer in women.
Epithelial ovarian cancer is the most common type of ovarian cancer. Rare types include germ cell tumours, stromal tumours and sarcomas. Primary peritoneal cancer is similar to epithelial ovarian cancer and is treated in the same way.
Epithelial ovarian cancer
Epithelial ovarian cancer is the most common type of ovarian cancer. About 90 out of 100 tumours of the ovary (90%) are epithelial.
Teratoma of the ovary
Ovarian teratoma is a type of germ cell tumour. Cancerous teratomas are rare, and usually affect girls and young women up to their early 20s.
Granulosa tumour of the ovary
Granulosa tumours are a type of sex cord stromal tumours. Less than 5 out of 100 women with ovarian cancer (5%) have this type.
Primary peritoneal cancer
Primary peritoneal cancer (PPC) is a rare cancer of the peritoneum. It is very similar to the most common type of ovarian cancer called epithelial cancer.
Fallopian tube cancer
Cancer of the fallopian tubes is rare. Only around 1 in 100 cancers (1%) of the female reproductive system are this type.
Borderline ovarian tumours
Borderline ovarian tumours are abnormal cells that form in the tissue covering the ovary. They are not cancer and are usually cured with surgery.
Read about the factors that can increase or reduce your risk of ovarian cancer. We don’t know what causes most ovarian cancers. But there are some factors that may increase your risk of developing it.
Possible risk factors for ovarian cancer
The following factors may increase the risk of ovarian cancer:
As with most cancers, the risk of developing ovarian cancer increases as you get older. Most cases of ovarian cancer happen are in women who have had their menopause.
Most ovarian cancers are due to gene changes that develop during a woman’s life and are not inherited. But between 5 and 15 out of 100 ovarian cancers (5 to 15%) are caused by an inherited faulty gene. Faulty inherited genes that increase the risk of ovarian cancer include BRCA1 and BRCA2. These genes also increase the risk of breast cancer.
If you are worried about your family history of ovarian cancer, speak to your doctor. They can tell you whether you need a referral to a genetics service.
Breast cancer and ovarian cancer can sometimes be due to the same faulty genes. Women who have had breast cancer have up to double the risk of developing ovarian cancer compared to other women in the population, and if their breast cancer was diagnosed before the age of 40, their risk is even higher.
If you think you may have a faulty gene, speak to your doctor.
Some older studies showed a link between taking fertility drugs and an increased risk of ovarian cancer. But more recent research doesn’t support this.
It is more likely that infertility itself increases ovarian cancer risk, rather than fertility treatment being the cause. More research is happening to clarify this.
Researchers looked at the risk of being overweight in premenopausal and postmenopausal women. They found that the risk of ovarian cancer was higher in premenopausal women with a BMI above 28, but there was no effect in postmenopausal women.
Ovarian cancer risk is higher in women who have a high BMI and have never used HRT. Women who have a high BMI and have used HRT have a lower risk of developing ovarian cancer.
Research has also found that taller women have a higher risk of ovarian cancer than shorter women.
Research has shown that women with endometriosis have an increase in their ovarian cancer risk compared to women who do not.
Smoking can increase the risk of certain types of ovarian cancer such as mucinous ovarian cancer. The longer you have smoked, the greater the risk.
For other types of ovarian tumours, such as clear cell and ovarian endometrioid cancer, how much smoking affects risk varies.
There has been a lot of research into the effect of dietary factors on ovarian cancer risk and so far most findings have been inconclusive and inconsistent. This may be because there is either no link between diet and ovarian cancer, or it is very small. Or it might be because of problems with the design of the studies.
Some studies have shown that a diet high in fats, particularly animal fats, may increase your risk of ovarian cancer. But more research is needed before we know whether changing our diet can reduce the risk of ovarian cancer.
Possible protective factors
The following factors may reduce your risk of ovarian cancer:
Taking the contraceptive pill at some point in your life reduces your risk of cancer of the ovary. Research has shown that the longer you take the pill, the more your risk is thought to come down. The reduction in risk lasts for at least 30 years after you stop taking the pill.
Having children seems to reduce the risk of ovarian cancer. The more children a woman has, the lower the risk.
Breastfeeding might lower the risk of ovarian cancer. This may be because your ovaries normally stop producing eggs each month while you are breastfeeding.
A study has shown that women who breastfed have a lower risk of getting ovarian cancer compared with women who never breastfed. The risk was lower in women who breast fed for a longer time.
Having your tubes tied because you don’t want any more pregnancies is called sterilisation. Two recent meta-analysis studies combined the results from all of the research looking at this. These studies both found that having your tubes tied reduces the risk of ovarian cancer.
Until recently, most research has shown that having your womb removed (hysterectomy) may also reduce your risk of ovarian cancer. But newer evidence suggests that there is a higher risk of ovarian cancer for women who have had a hysterectomy in recent years. Researchers think this might be because these days it is less common for younger women to have a hysterectomy. It may also be something to do with a change in the number of women having their ovaries removed, and the use of HRT after hysterectomy.
Non-starchy vegetables (such as broccoli, cabbage and onions) may decrease ovarian cancer risk but the evidence is uncertain.
Stories about potential causes are often in the media and it isn’t always clear which ideas are supported by evidence. There might be things you have heard of that we haven’t included here. This is because either there is no evidence about them or it is less clear.
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