Each month, follicles grow normally on the ovaries, according to Mayo Clinic. These follicles are cyst-like structures that produce progesterone and estrogen, which are both hormones; they also release an egg during ovulation. Problems arise when follicles continue growing and form functional cysts; cysts are classified as follicular or corpus luteum cysts.
Follicular cysts occurs when something goes awry during ovulation, notes Mayo Clinic. Normally, an egg bursts forth from the follicle and makes its way down the Fallopian tube, seeking to be fertilized by any awaiting sperm. When something is wrong, the follicle doesn't release the egg and instead starts to grow, forming a cyst.
Sometimes the ruptured follicle produces large quantities of the hormones progesterone and estrogen when it releases the egg. At this stage, the follicle is refereed to as the corpus luteum. When the egg seals itself off and fluid starts to pool inside the follicle instead, a cyst is formed.
Some other types of cysts are not formed as part of the normal menstrual cycle, advises Mayo Clinic. Dermoid cysts, for example, are a type of cyst that grows from the cells that normally produce human eggs. These cysts may contain tissues such as teeth, skin and hair. Cystadenomas are cysts that are made up of ovarian tissue. Usually, they are filled with mucous or watery liquid material.