A cyst is a fluid-filled sac. Every time a woman produces an egg from the ovary, it is surrounded by a tiny sac of fluid. This is a normal cyst, and rarely causes problems, but some women experience a slight stab of pain ('Mittelschmerz') in the region of the ovary as the fluid around the egg is released when ovulating in the middle of each month. If these normal tiny cysts reform and enlarge after releasing the egg, a true cyst of the ovary results. This is a 'follicle cyst', and these are quite common in teenage girls and young women.
They are usually less than 5 cm across, and may cause some irregularity of the periods. The woman is often not aware that the cyst is present unless it is discovered at surgery, or bursts. Occasionally they may form giant cysts the size of a football, and although a swelling similar to that of pregnancy may be noted in the abdomen, there still may be minimal pain or discomfort. If these cysts burst, the woman experiences sudden, severe pain on one side, low down in her abdomen. The pain eases slowly over several hours or days, as the irritating fluid contained in the cyst disperses, and no further treatment is necessary unless the cyst has been very large.
Women who are found to have follicle cysts, or who develop them frequently, can be given the oral contraceptive pill, which will prevent ovulation, and therefore the formation of further cysts. The pill will also shrink existing cysts, but large cysts will need to be removed surgically.
Many other types of ovarian cysts are known. These may be luteal cysts, which cause delayed or irregular periods; cysts caused by infections of the ovary and tubes; cysts associated with endometriosis; and in rare cases, cysts associated with some types of ovarian cancers.
The polycystic ovarian syndrome occurs when multiple small cysts form in one or both ovaries. The production of hormones by the ovaries is interfered with, and as a result the woman develops facial hairs, gains weight, stops her periods and is infertile. It is often discovered during investigations for infertility. Treatment of this syndrome involves cutting away part of the affected ovary tissue, and using hormones to stimulate the ovary to restart its correct function.