Normal Ovarian Function

In order to understand abnormal ovarian cysts one must first understand normal ovarian function. The ovary is responsible for making the female hormones as well as producing the eggs for pregnancy. The ovaries make cysts as part of their normal monthly cycle to form eggs. Cysts form to between 1-2 cm prior to ovulation. After ovulation a cyst remains to support pregnancy. If pregnancy does not occur that cyst goes away and a new cyst forms with the growing egg. When small cysts are seen on ultrasound, they are often a normal part of the life cycle of the ovary.

At the beginning of the menstrual cycle many tiny cysts begin to develop. One of these cysts will get a tiny head start and become the dominant follicle in which the egg develops. The mature follicle will be between 1-2 cm just prior to ovulation. When the egg becomes mature a signal gets sent from the brain to the ovary to induce ovulation.

Ovulation is the rupture of the dominant follicle which is a 1-2 cm cyst. The egg is expelled by the ovary where the fallopian tube is waiting to catch the egg. The egg travels down the fallopian tube where it hopes to meet up with a sperm and get fertilized. If fertilization occurs, the fertilized egg travels down the tube to the uterus and implants. This implanted fertilized egg then develops into a baby.

Once the dominant follicle ruptures it seals over and remains a cyst, usually about 2 cm in size. This cyst provides hormones for the egg in the hopes of fertilization. If the egg is fertilized the cyst becomes the corpus luteal cyst. This cyst will grow to about 2-3 cm and provide hormones for the developing baby until about 12 weeks of gestation when the fetus and placenta take over the production of hormones. If the egg does not get fertilized, this cyst goes away and the whole process starts over again.

Understanding this process explains why many times cysts seen on ultrasound are often considered normal. We call these normal cysts “physiologic cysts” because they represent normal physiology of the ovary. There are times when these processes can function incorrectly and produce a cyst that is not normal or physiologic. In these cases symptoms may be present but they may not. treatment for these abnormal cysts depends on a variety of issues.