How to Diagnose PCOS and Which Tests to Take?

Polycystic Ovary Syndrome (PCOS) is one of the most common endocrine disorders in women of reproductive age. Irregular cycles, skin breakouts, excessive hair growth, or difficulties conceiving often lead to suspicion of this diagnosis. However, identifying PCOS is not a quick process, and an ultrasound alone is insufficient for a verdict.

Modern diagnosis of polycystic ovaries requires a comprehensive approach. To establish an accurate diagnosis, a gynecologist-endocrinologist must correlate the patient's complaints, laboratory hormone test results, and instrumental study data, while excluding other similar pathologies.

In this practical guide, we will thoroughly examine the entire diagnostic pathway: from the first doctor's visit and symptom assessment to interpreting key criteria and tests.

First Step: Consulting a Specialist and Symptom Assessment

The path to understanding your body and making an accurate diagnosis always begins with the first and most important step—an in-person consultation with a specialist. Attempting to interpret random test results or match your symptoms with medical articles online is not only ineffective but also unsafe. PCOS is a complex endocrine disorder that can successfully mimic many other pathologies, so a professional assessment of the clinical picture is crucial.

At this stage, it is extremely important to determine which specific doctor to schedule an appointment with to save time and avoid unnecessary examinations. The initial consultation and detailed history taking lay the foundation for further laboratory and instrumental investigation, helping to create an individual diagnostic profile.

Which Doctor to See if PCOS is Suspected

If PCOS is suspected, it is crucial to choose the right specialist. Since PCOS is not merely a gynecological pathology but a complex multisystem endocrine-metabolic disorder, a standard examination by a classic gynecologist is often insufficient.

The primary physician who should manage a patient suspected of this syndrome is a gynecologist-endocrinologist. This specialist possesses deep knowledge at the intersection of two disciplines, allowing them to comprehensively assess both reproductive health and hormonal status.

If a highly specialized physician is unavailable, the diagnosis is conducted through the combined efforts of the following doctors:

• Obstetrician-Gynecologist — will perform the initial examination, conduct a pelvic ultrasound, and assess the nature of the menstrual cycle.
• Endocrinologist — will help identify associated metabolic disorders, such as insulin resistance, and rule out thyroid and adrenal gland pathology.

This interdisciplinary approach guarantees the accuracy of the examination and eliminates the risk of diagnostic errors.

Initial Examination and History Taking by a Gynecologist-Endocrinologist

The first visit to the gynecologist-endocrinologist begins with a detailed conversation. It is important for the doctor to reconstruct the complete picture of your health, so the history taking includes detailed questions:

• Menstrual Cycle Pattern: when the first period started (menarche), the cycle length, and whether there are delays of several months.
• Family History: whether any close female relatives suffered from infertility, PCOS, or type 2 diabetes.
• Weight Dynamics and Lifestyle: how body weight has changed recently, dietary habits, and level of physical activity.

After the interview, the specialist proceeds to a physical examination. They assess:

• Skin: presence of acne, oily seborrhea, and areas of hyperpigmentation in skin folds (acanthosis nigricans—a marker of insulin resistance).
• Hair Growth Pattern: excessive hair growth on the face, chest, and abdomen (hirsutism) according to the Ferriman-Gallwey scale.
• Body Mass Index (BMI): the ratio of height and weight to identify overweight or obesity.

The classic gynecological examination on the examination table allows the doctor to assess the condition of the genital organs and rule out other obvious pelvic pathologies before ordering instrumental diagnostics.

Understanding the Criteria: How Doctors Make a Diagnosis

After the gynecologist-endocrinologist has recorded the initial complaints and external manifestations, the key stage begins—correlating the obtained data with international medical standards. The diagnosis of "polycystic ovary syndrome" is never made based on a single symptom or a random ultrasound. It is a complex multisystem disorder requiring a strict systematic approach. To avoid overdiagnosis and confusing PCOS with temporary functional disorders, a clearly regulated algorithm is used in global practice. Doctors rely on criteria agreed upon by the scientific community, which allow for an objective assessment of the reproductive system and the issuance of an accurate, substantiated verdict.

What are the Rotterdam Diagnostic Criteria

The Rotterdam criteria are the gold standard for diagnosing Polycystic Ovary Syndrome, adopted by an international consortium of experts in 2003 in Rotterdam. Before their introduction, approaches to defining PCOS varied greatly across countries, leading to frequent diagnostic errors and confusion in prescriptions.

The essence of the Rotterdam consensus is the "two out of three" rule. For a gynecologist-endocrinologist to confidently confirm a PCOS diagnosis, the patient must present at least two of the following three signs:

1. Oligo- or anovulation — irregular menstrual cycles (intervals greater than 35 days) or complete absence of ovulation.
2. Hyperandrogenism — an excess of male sex hormones, confirmed by laboratory tests (elevated free testosterone and other androgens) or clinically (acne, hirsutism, hair loss on the head).
3. Polycystic Ovarian Morphology — specific changes in the organ's structure recorded during an ultrasound examination.

The most important condition for applying these criteria is the prior exclusion of other endocrine pathologies that have similar symptoms.

Three Main Signs for Confirming Polycystosis

Based on the "two out of three" rule, we will examine each of the three diagnostic pillars supporting PCOS verification in more detail:

1. Oligo- or anovulation (ovulation disorder). This condition manifests as an irregular menstrual cycle (delays, intervals longer than 35 days, fewer than 9 periods per year) or complete absence of menstruation (amenorrhea). Due to the lack of regular egg maturation and release, conception difficulties arise.
2. Hyperandrogenism (excess of male sex hormones). This can be clinical, when the physician observes external manifestations (excessive growth of coarse hair on the face and body—hirsutism, persistent acne, male-pattern baldness), or biochemical, confirmed by laboratory tests (elevated levels of free testosterone and other androgens in the blood).
3. Polycystic ovarian morphology on ultrasound. The ultrasound specialist records an increase in ovarian volume (more than 10 cubic centimeters) and the presence of multiple small follicles (12–20 in number, 2–9 mm in diameter), resembling a necklace.

For a diagnosis, a woman needs any two of these signs, provided other endocrine pathologies are excluded.

Laboratory Diagnostics: Which Tests Need to Be Performed

Based on the Rotterdam criteria, a physician cannot diagnose solely based on external signs. To confirm the excess of male sex hormones and rule out other endocrine pathologies, detailed blood laboratory testing is required. Tests allow a look inside the body's biochemical processes and reveal hidden markers of the syndrome. Laboratory diagnostics for suspected PCOS are built on two crucial pillars: assessment of sex hormones and examination of metabolic status. This comprehensive approach helps not only confirm the diagnosis but also determine the individual characteristics of the syndrome's course in a specific patient, which is critically important for selecting effective therapy.

Hormonal Profile: FSH, LH, Testosterone, and Androgens

Assessing the hormonal profile is a key stage in PCOS diagnosis, allowing confirmation of biochemical hyperandrogenism and evaluation of menstrual cycle regulation. All tests must be performed strictly on day 2–5 of the cycle (if present) in the morning on an empty stomach.

The mandatory laboratory minimum includes the following indicators:

• Total and free testosterone. Elevated free testosterone levels are the most accurate marker of androgen excess.
• SHBG (Sex Hormone-Binding Globulin). Its decrease is often observed in PCOS, leading to an increase in the active fraction of male hormones.
• Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH). High concentrations of LH and an altered LH/FSH ratio (often greater than 2:1) are characteristic of PCOS.
• Androstenedione and DHEA-S. These help differentiate ovarian versus adrenal origin of hyperandrogenism.

Additionally, the level of anti-Müllerian hormone (AMH) is assessed—in polycystic ovaries, its levels can exceed the norm several times due to the excess of antral follicles.

Assessment of Carbohydrate Metabolism and Glucose Tolerance Test

Insulin resistance is one of the key links in the pathogenesis of PCOS, found in over 70% of women with this diagnosis. Excess insulin directly stimulates the ovaries to produce more androgens, completing a vicious cycle. This is why assessing carbohydrate metabolism is mandatory when PCOS is suspected.

For detecting hidden disorders, the standard fasting glucose test is often insufficient. The physician prescribes a comprehensive examination:

• Fasting glucose and glycated hemoglobin (HbA1c) — basic markers for assessing the average blood sugar level over the last three months.
• Oral Glucose Tolerance Test (OGTT) — the "gold standard" for diagnosis. The patient fasts, then drinks a solution of 75g of glucose, and a repeat blood draw is taken after 2 hours.
• HOMA-IR Index — a calculated indicator of the ratio of fasting glucose and insulin levels, helping to confirm insulin resistance.

Timely performance of the OGTT allows for the early detection of glucose intolerance or undiagnosed type 2 diabetes, which is critically important for selecting the correct therapy and correcting nutrition.

Pelvic Ultrasound: What the Specialist Sees

Laboratory tests give the physician an understanding of the hormonal and metabolic status, but visualization is necessary for a complete picture. Pelvic ultrasound (US) is the "gold standard" of instrumental diagnostics when PCOS is suspected. This method allows a look inside to assess the anatomical changes in the reproductive system in real time.

During the scan, the specialist assesses not only the size of the uterus and ovaries but also their internal structure. It is important to understand that the ultrasound report is not a final diagnosis, but merely a description of the observed picture. The physician must correlate this data with clinical symptoms and test results to distinguish true pathology from temporary functional characteristics of the body.

Ultrasound Signs of Polycystic Ovaries

Pelvic ultrasound is one of the key stages in PCOS diagnosis. During the scan, which is preferably performed with a transvaginal probe on day 3–5 of the menstrual cycle, the specialist assesses the structure, size, and volume of the ovaries.

According to modern international guidelines and the Rotterdam criteria, the main sonographic signs of polycystic morphology are:

• Increased ovarian volume: The volume of at least one ovary exceeds 10 cm³ (provided there is no dominant follicle or corpus luteum).
• Multiple small follicles: The organ structure visualizes 20 or more follicles with a diameter from 2 to 9 mm. When using older generation ultrasound equipment, a criterion of 12 follicles is permissible.
• Specific arrangement ("string of pearls sign"): The follicles are often located around the periphery of the ovary, surrounding a thickened, hyperechoic central part (stroma).

It is important to remember that the ultrasound report is not a final diagnosis, but only describes the organ's morphology.

Distinguishing PCOS from Multifollicular Ovaries (MFO)

The main error in ultrasound diagnostics is confusing PCOS with multifollicular ovaries (MFO). MFO is not a diagnosis, but a temporary ultrasound feature that is often a variant of normal (for example, in young girls, due to exhaustion, or after stopping contraceptives).

Here are the key differences that help the gynecologist-endocrinologist draw the line between normal and pathological:

Parameter	Multifollicular Ovaries (MFO)	Polycystic Ovary Syndrome (PCOS)
Ovary Volume	Normal (usually up to 10 cm³)	Enlarged (more than 10 cm³)
Follicle Location	Chaotic, throughout the ovarian tissue	Peripheral (the "necklace" sign)
Stroma Condition	Normal density and volume	Dense, thickened capsule
Ovulation	Preserved (regular cycle)	Absent or occurs rarely
Symptoms	Absent	Hyperandrogenism, acne, hirsutism

MFOs do not require treatment if the menstrual cycle is regular and there are no complaints. PCOS, however, is a systemic endocrine syndrome requiring mandatory monitoring.

Differential Diagnosis: Excluding Similar Pathologies

Diagnosing PCOS is not simply about noting changes in the ovaries on ultrasound or detecting elevated testosterone levels. Since the key symptoms of the syndrome, such as irregular cycles, acne, and excessive hair growth, are not unique, thorough differential diagnosis is crucial. Many endocrine disorders can skillfully mimic polycystic ovaries, leading the physician down the wrong path.

Without excluding these "imitators," there is a huge risk of initiating ineffective therapy. This is why the final verdict is reached by exclusion, when the specialist systematically checks the function of other endocrine glands to confirm the true cause of the hormonal imbalance.

Diseases Mimicking PCOS Symptoms

Because the clinical manifestations of PCOS are highly diverse, it is important for the physician to avoid overdiagnosis. Many endocrine pathologies successfully "mask" as polycystic ovaries, requiring a fundamentally different treatment. The diagnosis of PCOS is always a diagnosis of exclusion.

The main pathologies that the gynecologist-endocrinologist must rule out first:

• Nonclassical Congenital Adrenal Hyperplasia (CAH). This is a genetic disorder of adrenal hormone production that presents with pronounced hyperandrogenism. A test for 17-OH-progesterone is mandatory for differentiation.
• Hyperprolactinemia. Elevated prolactin levels directly block ovulation and disrupt the menstrual cycle, mimicking the clinical picture of PCOS.
• Thyroid Dysfunction. Both hypothyroidism and hyperthyroidism can cause oligomenorrhea and anovulatory cycles. Assessing TSH levels is an essential diagnostic step.
• Cushing's Syndrome. Excessive cortisol production by the adrenal glands leads to rapid weight gain, hirsutism, and cycle disturbances.

Only after the specialist has excluded these "masks" can the final stage of confirming Polycystic Ovary Syndrome begin.

The Correct Algorithm for Final Diagnosis

Establishing a final PCOS diagnosis is always a sequential process that requires strict adherence to the clinical protocol. An experienced gynecologist-endocrinologist will never rush this diagnosis based solely on one pelvic ultrasound.

The correct algorithm for verifying the diagnosis is as follows:

1. History Taking and Symptom Documentation. The physician assesses menstrual cycle regularity (identifying chronic anovulation or infrequent menstruation) and external signs of androgen excess (acne, hirsutism).
2. Laboratory Stage. Blood tests for sex hormones (free testosterone, luteinizing hormone, follicle-stimulating hormone) are performed to confirm biochemical hyperandrogenism.
3. Exclusion of Alternative Pathologies. TSH, prolactin, and 17-OH-progesterone levels are assessed to rule out thyroid diseases, hyperprolactinemia, and nonclassical CAH.
4. Instrumental Diagnostics. A pelvic ultrasound is performed. It is important for the specialist to distinguish PCOS from transient multifollicular ovaries.
5. Metabolic Status Assessment. A glucose tolerance test is ordered to detect associated insulin resistance or carbohydrate metabolism disorders.
6. Verdict Issuance. The diagnosis is definitively confirmed if the patient presents with at least two of the three criteria established by the Rotterdam criteria, and only after all other endocrine disorders have been completely excluded.

Conclusion

Diagnosing Polycystic Ovary Syndrome (PCOS) is always a complex, multi-stage process that does not tolerate hasty conclusions. As medical practice shows, no single diagnostic method can be sufficient grounds for a verdict. A diagnosis cannot be made solely based on pelvic ultrasound results or on elevated androgen levels alone.

The path to an accurate diagnosis always lies through the Rotterdam criteria, which require the identification of at least two of three features: anovulation, clinical or laboratory hyperandrogenism, and the characteristic ultrasound pattern of polycystic ovaries. Crucially, the differential diagnosis remains key—ruling out thyroid, adrenal, and hyperprolactinemia disorders that can skillfully mimic PCOS symptoms.

If you notice irregular cycles, excessive hair growth, persistent acne, or are having difficulty conceiving, do not delay visiting a gynecologist-endocrinologist. Timely consultation and basic screening, including hormonal profile assessment and a glucose tolerance test, will help identify the problem early and prevent long-term consequences such as insulin resistance, type 2 diabetes, and cardiovascular diseases.

PCOS is not a sentence, but a metabolic and endocrine characteristic of the body that can and should be successfully managed. Modern treatment protocols allow for effective symptom control, ovulation restoration, healthy pregnancy planning, and maintaining a high quality of life for many years. The main thing is to take the first step toward conscious self-care and entrust your health to qualified specialists.