How PCOS Is Diagnosed

No two women with polycystic ovary syndrome (PCOS) have the exact same symptoms. This makes PCOS diagnosis challenging, as does the fact that many other conditions can present similarly. Because of this, an ultimate diagnosis of PCOS heavily relies on ruling out other possible causes. To be formally diagnosed with PCOS, you must meet two of the following diagnostic criteria:

1. Irregular or absent periods
2. Biological or physical signs of hyperandrogenism (high androgen level) without another medical cause
3. A string of small follicles (cysts) on an ultrasound examination

These guidelines, referred to as the Rotterdam Criteria, are the ones most commonly used by endocrinologists in the United States and abroad.

Physical Examination

Your doctor will do a complete physical and pelvic exam and look for physical signs of high androgens—like testosterone-induced hair growth (specifically on the face, lower abdomen, back, chest, and nipples). Other signs may include acne, skin tags, male pattern baldness, and acanthosis nigricans (darkened, thick skin on the neck, thighs, armpits, or vulva).

When a woman has infrequent, absent, or irregular periods (eight or fewer cycles per year), it is a sign that ovulation may not be occurring and could indicate PCOS.

Your doctor will ask you about any unusual symptoms you may have noticed, so make sure to mention any of your concerns.

Writing a list before you go may help you remember important points to ask about. This may include specific facts and figures about the frequency of periods, when they occurred, what happened when you had them, and what other symptoms you had between periods. This can help your doctor determine if you are ovulating.

Lab Tests

Blood work will most likely be taken. Besides hormonal testing, like for testosterone, other sex hormones should be checked such as follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin. Your doctor may test for other associated conditions like high cholesterol and insulin resistance.

A newer blood test, which evaluates the anti-Mullerian hormone (AMH) in women, is now being used by some physicians as a diagnostic tool as well.

Transvaginal Ultrasound

A transvaginal ultrasound may or not be performed to rule out PCOS. In a transvaginal ultrasound probe is placed inside the vagina, which allows the physician to examine the reproductive organs and look for abnormalities. The thickness of the endometrium can be measured.

Oftentimes these follicles are called cysts. There are many women who have cystic-appearing ovaries without symptoms of hyperandrogenism, and many women who have been diagnosed with PCOS who do not have classically cystic ovaries.

Some doctors find the use of transvaginal ultrasound in adolescents unnecessary. 

Endometrial Biopsy

An endometrial biopsy can be performed to determine if your endometrial tissue is in the correct phase or to test for endometrial cancer, which is seen more frequently in those with PCOS. This risk of endometrial cancer increases with the number of and length of time between missed periods.

The biopsy can be done in your doctor’s office and is relatively painless, although you may experience minimal cramping during the procedure. A small amount of tissue is removed from your uterus through a thin catheter placed into through the cervix and into the uterus. This tissue is then analyzed in the context of your cycle and examined for cancer cells.

Differential Diagnoses

Your doctor will look for other conditions in which irregular menstruation is common, such as thyroid disease, hyperprolactinemia, Cushing's syndrome, and congenital adrenal hyperplasia.

In thyroid disease, either too little or too much thyroid hormone can disrupt the menstrual cycle and lead to changes in body weight. Thyroid hormone testing is done to look for these conditions.

Hyperprolactinemia is an increased production of the prolactin hormone by the pituitary gland. This hormone stimulates the production of breast milk, and it may also be increased in PCOS. A magnetic resonance imaging (MRI) scan may be done to look for growths on the pituitary gland.

Cushing's syndrome results when a benign tumor on the pituitary gland or adrenal glands causes too much cortisol and androgens to be produced. The symptoms can be much like PCOS. Diagnostic tests for this disorder include urine and saliva cortisol tests, as well as a dexamethasone suppression test.

Classical adrenal hyperplasia (CAH) is an enzyme deficiency in the adrenal glands that leads to the excessive production of DHEA-S (an androgen) and a lack in the production of cortisol and aldosterone, the other main adrenal hormones; this is usually diagnosed at birth. However, a condition called non-classical adrenal hyperplasia is the version of this condition that is very similar to PCOS. It leads to the production of the same hormone (DHEA-S), but patients still produce normal amounts of cortisol and aldosterone so it can go undiagnosed until adulthood. The screening test is for a hormone called 17-hydroxyprogesterone that is measured in the morning.

Other conditions that may need to be excluded, depending on your symptoms, include pregnancy, hypothalamic amenorrhea, and primary ovarian insufficiency.

A Word From Verywell

It can take persistence to reach a diagnosis of PCOS, as it is known to be underdiagnosed or misdiagnosed. Seek a second opinion if your diagnosis is not clear. While this may all seem overwhelming, remember that you are not alone. As the most common endocrine disorder among women of childbearing age, there are many women with PCOS who have been through this. Reach out to a support group and the people who care about you. Following your doctor's advice and learning about your disease are the best ways to manage it.