The dark spots on an ultrasound that give polycystic ovary syndrome its name are not actually cysts. They are small, immature egg follicles that stalled partway through development and never released an egg. A true ovarian cyst is a fluid-filled sac, often arising from a follicle that ovulated or failed to resolve on its own. The follicles seen in PCOS are structurally and clinically different, and a 2025 study in JAMA Internal Medicine confirmed that women with PCOS are no more likely than women without PCOS to develop genuine ovarian cysts of any common type. That distinction matters for diagnosis, treatment, and how you think about the condition overall.
Why the Name Is Misleading
When ultrasound imaging became widely available in the 1980s, clinicians noticed that many women with irregular periods and excess androgens had ovaries dotted with small, round structures arranged in a ring-like pattern. These were labeled “cysts,” and the syndrome inherited the name. In reality, each of those structures is a follicle, the tiny fluid-filled compartment where an egg develops each month. In a typical cycle, one follicle grows dominant, releases its egg, and the others are reabsorbed. In PCOS, that selection process breaks down. Many follicles begin to grow but none wins the race, leaving a crowd of stalled follicles sitting at the periphery of the ovary.
The JAMA Internal Medicine study, which compared women with and without PCOS, found that PCOS was associated with roughly 12-fold higher odds of having a multifollicular ovary and about 12-fold higher odds of an ovarian volume exceeding 10 mL. But when researchers looked at dominant follicles, endometriomas, simple cysts, paraovarian cysts, hemorrhagic cysts, and dermoid cysts, there was no difference between the two groups.1JAMA Network. Ovarian Cysts in Polycystic Ovary Syndrome In other words, PCOS gives you more follicles, not more cysts. The condition’s name has stuck for historical reasons, but it actively misleads patients into thinking they have dangerous growths on their ovaries.
What Causes Follicles to Stall
The follicular arrest behind PCOS traces back to excess androgens. Androgens are hormones that all women produce in small amounts, but in PCOS those levels climb high enough to disrupt the delicate sequence of follicle growth and ovulation.2PubMed Central. Decoding androgen excess in polycystic ovary syndrome: Roles of insulin resistance and other key intraovarian and systemic factors The excess androgens interfere with the signals that normally allow one follicle to become dominant. Instead, multiple follicles grow to a small size, stall, and accumulate.
Insulin resistance is a major driver of that androgen excess. When your body’s tissues become less responsive to insulin, the pancreas compensates by producing more of it. The ovaries and adrenal glands remain sensitive to insulin even when other tissues do not, so they respond to the extra insulin by ramping up androgen production.3PubMed Central. Role of insulin and insulin resistance in androgen excess disorders This creates a reinforcing loop: insulin resistance drives androgen production, and elevated androgens can worsen metabolic function. Not every woman with PCOS has measurable insulin resistance, but the overlap is large enough that it shapes how clinicians approach treatment.4PubMed Central. Association of Insulin Resistance and Elevated Androgen Levels with Polycystic Ovarian Syndrome (PCOS): A Review of Literature
How PCOS Is Actually Diagnosed
Finding multiple follicles on ultrasound is only one piece of the puzzle. The most widely used diagnostic framework, the Rotterdam criteria, requires two out of three features: irregular or absent ovulation, clinical or lab evidence of excess androgens, and polycystic-appearing ovaries on imaging. You can be diagnosed with PCOS without having the characteristic ovarian appearance, and you can have polycystic-looking ovaries without having PCOS. This is another reason the name causes confusion.
Ultrasound thresholds have been updated as imaging technology has improved. Older scanners set the bar at 12 follicles per ovary, but newer, higher-resolution equipment picks up more follicles in healthy women too. Research using modern scanners found that a threshold of 26 follicles across the entire ovary provided a better balance of sensitivity and specificity for distinguishing PCOS from healthy controls. An ovarian volume of 10 cubic centimeters remained a useful secondary marker.5PubMed. Updated ultrasound criteria for polycystic ovary syndrome: reliable thresholds for elevated follicle population and ovarian volume
These thresholds also change with age. In women under 25, the best cutoffs may be 12 mL for volume and 13 follicles, while in women aged 35 to 39 the numbers drop to about 8 mL and 10 follicles.6PubMed Central. Polycystic Ovary Morphology: Age-Based Ultrasound Criteria Younger women naturally have more antral follicles, so applying a single threshold across all ages leads to overdiagnosis in younger patients and underdiagnosis in older ones.
AMH as an Alternative to Ultrasound
Anti-Müllerian hormone (AMH) is produced by the small growing follicles in the ovaries, and its blood level roughly mirrors the follicle count. Women with PCOS tend to have AMH levels several times higher than average, because they have many more of those small follicles. One study found AMH levels about three times higher in women with PCOS than in controls, and proposed that AMH could be used as a stand-in for follicle count when reliable ultrasound data are unavailable.7The Journal of Clinical Endocrinology & Metabolism. Serum Anti-Müllerian Hormone as a Surrogate for Antral Follicle Count for Definition of the Polycystic Ovary Syndrome More recent work has found that an AMH level above about 5 ng/mL offers high sensitivity and specificity for identifying polycystic ovarian morphology.8Human Reproduction. Diagnosis of polycystic ovary syndrome (PCOS): revisiting the threshold values of follicle count on ultrasound and of the serum AMH level for the definition of polycystic ovaries This is especially useful for adolescents, where transvaginal ultrasound may not be appropriate and transabdominal imaging is less precise.
Symptoms That Have Nothing to Do with the Ovaries
Many people think of PCOS as an ovarian condition, but its effects reach well beyond the pelvis. The androgen excess that causes follicular arrest is the same androgen excess behind the skin and hair symptoms that often bother women more than anything happening inside the ovaries. These include acne, excess hair growth on the face and body (hirsutism), and thinning hair on the scalp, along with darkened skin patches in body folds known as acanthosis nigricans.9PubMed. Diagnosis and management of the dermatologic manifestations of the polycystic ovary syndrome
Hirsutism and acne do not always travel together, and they reflect slightly different androgen profiles. Women with hirsutism tend to have higher levels of ovarian and adrenal androgens, more obesity, and more insulin resistance, while acne alone correlates with a narrower slice of androgen activity.10PubMed. Acne and hirsutism in polycystic ovary syndrome: clinical, endocrine-metabolic and ultrasonographic differences Irregular periods or absent periods typically begin around the time of puberty and are often dismissed as normal variation in adolescence, delaying diagnosis for years.11PubMed. Menstrual disorders in adolescents. Excess androgens and the polycystic ovary syndrome
Mental health effects are also common. The hormonal disruption, the visible skin symptoms, weight gain that resists conventional dieting, and fertility concerns all contribute to higher rates of anxiety and depression among women with PCOS.12PubMed Central. The Invisible Struggle: The Psychosocial Aspects of Polycystic Ovary Syndrome These are not secondary complaints. For many women, the psychological burden is the part of PCOS that most affects daily life.
Conditions That Look Like PCOS
Before settling on a PCOS diagnosis, clinicians need to rule out other conditions that produce similar symptoms. The closest mimic is nonclassical congenital adrenal hyperplasia (NCCAH), a genetic condition in which the adrenal glands overproduce androgens. About a fifth of women being evaluated for PCOS also show elevated levels of 17-hydroxyprogesterone, the hormone used to screen for NCCAH.13PubMed Central. Polycystic Ovary Syndrome and NC-CAH: Distinct Characteristics and Common Findings. A Systematic Review A stimulation test can help separate the two, and research has identified that a baseline 17-hydroxyprogesterone level above 5.4 ng/mL has very high specificity for NCCAH, which can reduce the need for that extra test in clear-cut cases.14The Journal of Clinical Endocrinology & Metabolism. Steroid Screening Tools Differentiating Nonclassical Congenital Adrenal Hyperplasia and Polycystic Ovary Syndrome Other conditions on the differential include thyroid disorders, high prolactin levels, and Cushing syndrome, all of which can disrupt ovulation and raise androgen levels.
Fertility and Ovulation Induction
PCOS is one of the most common causes of difficulty getting pregnant, but the prognosis is generally good with treatment because the ovaries still contain plenty of eggs. The problem is getting one to release. For women who are overweight, weight loss through diet and exercise can restore ovulation without medication. Research has shown that even modest reductions in central body fat improve insulin sensitivity enough to restart normal cycles in some women.15The Journal of Clinical Endocrinology & Metabolism. Restoration of Reproductive Potential by Lifestyle Modification in Obese Polycystic Ovary Syndrome: Role of Insulin Sensitivity and Luteinizing Hormone
When lifestyle changes are not enough, medication is the next step. Letrozole has overtaken clomiphene citrate as the preferred first-line ovulation induction drug for PCOS. A large multicenter trial found that women who received letrozole had cumulative live birth rates of about 28%, compared with roughly 19% for clomiphene.16PubMed Central. Letrozole versus clomiphene for infertility in the polycystic ovary syndrome A systematic review and meta-analysis confirmed the pattern, showing that letrozole improved ovulation rates, clinical pregnancy rates, and live birth rates compared with clomiphene across multiple trials.17PubMed. Letrozole Compared With Clomiphene Citrate for Polycystic Ovarian Syndrome: A Systematic Review and Meta-analysis
For women who do not respond to oral medications, laparoscopic ovarian drilling is an option. The procedure involves making small burns or laser holes in the ovarian surface to reduce androgen-producing tissue. It has been used since the 1980s and offers pregnancy and live birth rates comparable to gonadotropin injections, without the risks of ovarian hyperstimulation or multiple pregnancies that come with injectable hormones.18PubMed Central. Laparoscopic ovarian drilling: An alternative but not the ultimate in the management of polycystic ovary syndrome IVF remains an option for cases that do not respond to any of these approaches.
Managing Symptoms When Pregnancy Is Not the Goal
For women not trying to conceive, treatment focuses on managing androgen-driven symptoms and protecting long-term metabolic health. Combined oral contraceptive pills are standard for regulating periods, reducing acne, and suppressing excess hair growth. They work by lowering circulating androgen levels and providing the regular progesterone withdrawal that prevents the uterine lining from building up unchecked.
Metformin takes a different approach, targeting insulin resistance. A systematic review found that metformin was better than oral contraceptives for metabolic outcomes, especially in women with a BMI of 25 or above. Oral contraceptives were better for cycle regularity and, in leaner women, for improving hirsutism. The combination of both was more effective for lowering androgen levels and insulin resistance than either alone.19The Journal of Clinical Endocrinology & Metabolism. Metformin and Combined Oral Contraceptive Pills in the Management of Polycystic Ovary Syndrome: A Systematic Review and Meta-analysis One long-term trial in adolescents found that over two years, metformin led to significant weight loss and improved insulin levels, while oral contraceptives caused a slight weight gain and worsened metabolic markers.20Middle East Fertility Society Journal. Randomized controlled trial of the effects of metformin versus combined oral contraceptives in adolescent PCOS women through a 24 month follow up period This trade-off matters when choosing a treatment path, because PCOS is a chronic condition and the metabolic trajectory over years and decades is at least as important as symptom control in the short term.
Long-Term Health Risks
The metabolic disruption in PCOS is not just a background detail of the diagnosis. It carries real cardiovascular and cancer risks over time. A systematic review and meta-analysis found that women with PCOS had higher rates of type 2 diabetes and hypertension compared with women without the condition, along with a higher risk of non-fatal stroke.21Human Reproduction Update. Long-term cardiometabolic disease risk in women with PCOS: a systematic review and meta-analysis The constellation of abdominal obesity, abnormal cholesterol, insulin resistance, and high blood pressure that clusters in PCOS collectively raises cardiovascular risk, and women with higher androgen levels seem to carry the greatest burden.22PubMed Central. Women with PCOS have a heightened risk of cardiometabolic and cardiovascular diseases: statement from the Experts Group on Inositol in Basic and Clinical Research and PCOS (EGOI-PCOS) and Italian Association of Hospital Cardiologists (ANMCO)
Endometrial cancer risk also increases in PCOS. When ovulation does not occur, the uterine lining builds up month after month under the influence of estrogen without the counterbalancing effect of progesterone. A meta-analysis found that women with PCOS had roughly four times the odds of developing endometrial cancer. When the analysis was restricted to premenopausal women, the odds rose to about five times higher.23PubMed Central. Risk of endometrial cancer in patients with polycystic ovarian syndrome: A meta‑analysis This is one of the reasons clinicians prescribe oral contraceptives or periodic progesterone even for women who are not sexually active: the goal is to ensure the uterine lining sheds regularly.
Ovarian Torsion and Enlarged Ovaries
While PCOS does not cause true cysts, the enlarged ovarian volume that comes with a multifollicular ovary raises a separate structural concern: torsion. Ovarian torsion happens when an ovary twists on its blood supply, cutting off circulation. It is a surgical emergency. A review investigating the link between PCOS and torsion identified 14 published cases and concluded that significantly enlarged polycystic ovaries could be a meaningful risk factor. The most common presentation was acute lower abdominal pain in a woman already known to have polycystic ovaries.24PubMed Central. Ovarian Torsion in Polycystic Ovary Syndrome: A Potential Threat? Torsion remains uncommon, but it is worth knowing about, especially because PCOS patients and their doctors may assume that sudden pelvic pain is just another aspect of the syndrome and delay evaluation.
Genetics, Environment, and Why PCOS Is So Common
PCOS runs in families, and research confirms a strong genetic component. Multiple genes involved in hormone signaling, insulin action, inflammation, and energy balance have been linked to the syndrome. Yet no single gene variant has been found to fully explain it; PCOS is polygenic, meaning it results from the combined effects of many small genetic contributions interacting with the environment.25PubMed Central. Genetic Basis of Polycystic Ovary Syndrome (PCOS): Current Perspectives Family studies show that female relatives of women with PCOS are more likely to have the syndrome themselves, while male relatives often show metabolic features like insulin resistance and abnormal lipid levels.26PubMed Central. Genetics of polycystic ovary syndrome
Environmental chemicals may also play a role. Endocrine-disrupting compounds found in plastics, pesticides, and personal care products can mimic or interfere with hormones. Research suggests that prenatal exposure to these compounds could alter fetal programming in ways that favor PCOS development later in life, and that ongoing exposure might accelerate the syndrome in people who are already genetically predisposed.27PubMed. Polycystic ovary syndrome (PCOS) and endocrine disrupting chemicals (EDCs) The evidence here is still emerging and relies heavily on animal models, but it raises important questions about whether the rising prevalence of PCOS in modern populations reflects more than just better diagnosis.
From an evolutionary standpoint, the sheer prevalence of PCOS (affecting roughly one in ten women worldwide) has puzzled researchers. A condition that impairs fertility should, in theory, become rare over generations. One hypothesis is that the metabolic profile of PCOS, which efficiently stores energy and resists insulin’s fat-clearing effects, was advantageous during the long stretches of human history when food was scarce and unpredictable. Women with this metabolic pattern may have been better at maintaining fertility through famines and seasonal food shortages. In modern environments defined by caloric excess and sedentary lifestyles, that same metabolic wiring becomes a liability, tipping into the full syndrome.28Evolution, Medicine, and Public Health. Evolutionary origins of polycystic ovary syndrome: An environmental mismatch disorder 29PubMed. Type 2 diabetes, cardiovascular disease, and the evolutionary paradox of the polycystic ovary syndrome: a fertility first hypothesis This “environmental mismatch” framing does not change your treatment plan, but it reframes PCOS as something other than a defect: a set of traits tuned to a world that no longer exists.