Ovarian cysts in young females are overwhelmingly caused by the normal hormonal activity of the menstrual cycle. These “functional” cysts form as a routine part of ovulation and are the most common type by far. The occurrence of ovarian cysts increases with age during puberty, ranging from about 4% to 31% throughout adolescence, with the highest incidence around age 15. In most cases, they resolve on their own within a few weeks without any treatment.
That said, not every ovarian cyst is a simple byproduct of a normal cycle. Hormonal conditions, endometriosis, certain types of birth control, infections, and even developmental factors present from birth can all play a role.
How Normal Cycles Produce Cysts
Each menstrual cycle, a small sac called a follicle grows inside one of the ovaries. Its job is to nurture and release an egg. Two things can go wrong in this otherwise routine process, and both produce what doctors call functional cysts.
A follicular cyst forms when the follicle doesn’t rupture to release the egg. Instead, it keeps growing and fills with fluid. These cysts are typically thin-walled and fluid-filled, and they usually disappear on their own within one to three cycles.
A corpus luteum cyst forms after ovulation. Once the egg is released, the empty follicle normally transforms into a temporary structure called the corpus luteum, which produces progesterone to prepare the uterus for a possible pregnancy. If no pregnancy occurs, the corpus luteum breaks down within 10 to 12 days. Sometimes, though, it seals shut and fills with fluid or blood, especially if a small blood vessel on the ovary’s surface gets disrupted during ovulation. This creates a cyst that can grow larger and cause more noticeable symptoms than a follicular cyst, but it still typically resolves without intervention.
These two types account for the vast majority of ovarian cysts in young females. They’re not a sign of disease. They’re a sign that the reproductive system is active.
Polycystic Ovary Syndrome (PCOS)
PCOS is one of the most common hormonal conditions in young women and a well-known cause of ovarian cysts. Despite the name, the “cysts” in PCOS are actually multiple small follicles that started developing but never matured enough to release an egg. They accumulate on the ovaries over time.
PCOS is driven by higher-than-normal levels of androgens (often called “male hormones,” though all women produce them in small amounts). This hormonal imbalance disrupts ovulation, which is why irregular or absent periods are a hallmark symptom. Other signs include acne, excess facial or body hair, and weight gain.
Diagnosing PCOS in teenagers is tricky because irregular periods and multi-follicular ovaries are a normal part of puberty. The international guidelines updated in 2018 now recommend that, for adolescents specifically, a diagnosis should require both irregular ovulation and evidence of excess androgens. Ultrasound findings of multiple follicles alone aren’t enough in this age group, because they can look identical to normal pubertal ovaries.
Endometriomas From Endometriosis
Endometriosis occurs when tissue similar to the uterine lining grows outside the uterus. When this tissue implants on or near an ovary, it can form a specific type of cyst called an endometrioma, sometimes referred to as a “chocolate cyst” because it fills with old, dark blood.
The leading theory is that menstrual blood flows backward through the fallopian tubes and deposits endometrial cells into the pelvic cavity. When these cells land on the ovary’s surface, they secrete enzymes that break down surrounding tissue, allowing them to burrow in. Over time, the ovarian surface folds inward, creating a pocket that fills with blood from the trapped endometrial tissue. Ovarian fluid may also encourage these displaced cells to grow.
Endometriomas tend to cause more persistent pain than functional cysts, particularly during periods or intercourse. While endometriosis is often thought of as an adult condition, it is increasingly recognized in adolescents and young women, especially those with severe menstrual pain that doesn’t respond well to standard pain relief.
Dermoid Cysts and Other Growths
Not all ovarian cysts come from the menstrual cycle. Dermoid cysts (also called mature cystic teratomas) are a type of benign growth that develops from egg cells. Because egg cells have the potential to become any type of tissue, these cysts can contain unexpected material like hair, skin, fat, or even teeth. They grow slowly and can be present for years before being discovered.
Dermoid cysts don’t resolve on their own. They’re typically removed surgically if they reach a size that poses risk. Cysts larger than 5 to 6 centimeters raise concern because they increase the chance of ovarian torsion, where the ovary twists on itself and cuts off its own blood supply. Minimally invasive surgery is usually the approach for smaller cysts, while cysts larger than 12 centimeters may require a more traditional open procedure. For young women, surgeons generally aim to remove only the cyst and preserve as much healthy ovarian tissue as possible.
Birth Control and Medication Effects
Certain types of hormonal birth control can actually promote cyst formation rather than prevent it. Progestin-only methods, including the mini-pill and some implants, suppress one of the two key hormones involved in ovulation (luteinizing hormone) while allowing the other (follicle-stimulating hormone) to continue working. The result is that follicles start developing but don’t fully mature or release an egg, sometimes forming fluid-filled cysts instead.
These medication-related cysts are common but usually painless. Roughly one in six causes noticeable discomfort. They tend to resolve once the medication is stopped or the body adjusts. Combined hormonal contraceptives (those containing both estrogen and progestin) are less likely to cause this issue because they suppress both hormones involved in follicle development.
Pelvic Infections
Pelvic inflammatory disease, usually caused by sexually transmitted bacteria, can lead to inflammatory masses on or near the ovaries. When infection spreads from the cervix or uterus up to the fallopian tubes and ovaries, it can create a tubo-ovarian abscess: a pocket of infected fluid involving the tube and ovary together. This isn’t a cyst in the traditional sense, but it can look like one on an ultrasound and cause significant pain, fever, and tenderness in the lower abdomen.
Unlike functional cysts, these masses require prompt treatment with antibiotics and sometimes hospital observation. Left untreated, they can affect future fertility.
Cysts Present From Birth
Some ovarian cysts develop before a baby is even born. Fetal ovarian tissue responds to the mother’s hormones during pregnancy, and elevated levels of certain pregnancy hormones or conditions like maternal diabetes can stimulate cyst formation in the developing ovaries. These cysts are sometimes detected on prenatal ultrasounds during the third trimester. Most resolve on their own in the first few months of life as the influence of maternal hormones fades, though larger ones occasionally require monitoring or intervention in the newborn period.
When Cysts Cause Symptoms
Most ovarian cysts produce no symptoms at all and are found incidentally during an ultrasound for something else. When they do cause problems, the most common complaint is a dull ache or pressure on one side of the lower abdomen. A cyst that ruptures can cause sudden, sharp pain that resolves within hours to days. Some women notice bloating, a feeling of fullness, or irregular bleeding.
The most serious complication is ovarian torsion, which is more common in younger patients and in those with cysts over 5 to 6 centimeters. Torsion causes sudden, severe pain in the lower abdomen or flank, often accompanied by nausea and vomiting. The pain may come in waves, with episodes of intense discomfort followed by partial relief, which can make it hard to distinguish from other causes of abdominal pain like appendicitis. Torsion is a surgical emergency because the twisted blood supply can permanently damage the ovary if not corrected quickly.
How Cysts Are Evaluated
Pelvic ultrasound is the primary tool for evaluating ovarian cysts. A simple, fluid-filled cyst with thin walls and no internal structures is almost always benign, and in young women, the overwhelming majority fall into this category. Complex cysts, those with solid areas, thick walls, internal divisions, or blood flow visible on ultrasound, get closer attention because they may represent a dermoid, endometrioma, or rarely something more concerning.
In young females, ovarian cancer is extremely rare, so the threshold for concern is different than in older women. A single ultrasound sometimes can’t distinguish between a functional cyst and other types of simple cysts, so a follow-up scan after one or two menstrual cycles is common. If a functional cyst is the cause, it will typically have shrunk or disappeared by then. Cysts that persist, grow, or have complex features are more likely to need further evaluation or removal.