Understanding Your Lab Tests for Polycystic Ovary Syndrome (PCOS)

Is It PCOS or Another Health Condition?

Nurse taking blood from patient, close up
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If you have polycystic ovary syndrome (PCOS), you may be experiencing any number of symptoms, like irregular menstrual cycles or signs of high androgen levels like acne and abnormal hair growth (hirsutism). If you stop menstruating and/or your doctor suspects a diagnosis of PCOS, a number of blood tests are classically run to ensure that something else isn't going on, like an underactive thyroid gland or a rare androgen-secreting tumor.

Putting the Pieces Together

It's important to note that your history and physical exam are helpful in making the diagnosis of PCOS, and your doctor will use both your blood tests and your exam to piece together the diagnosis. As of now, there's no single slam-dunk blood test to diagnose PCOS, so your doctor will likely do a pelvic exam and perhaps an ultrasound along with your blood tests to rule out other illnesses behind your symptoms.

In addition, remember that if you've missed your period or stopped menstruating, you can bet that the first test your doctor will do is a pregnancy test, so don't be surprised about this, even if you're certain you're not pregnant. After that's confirmed negative, your doctor will move forward with other blood tests.

FSH/LH Blood Test

Follicle stimulating hormone (FSH) and luteinizing hormone (LH) are produced and released by the pituitary gland, a pea-sized gland located at the base of your brain.

FSH stimulates the growth of an egg follicle within the ovary, while the surge of LH triggers the release of the egg during ovulation. 

Previous diagnoses of PCOS were made based on an LH to FSH ratio of greater than 3:1. This is not the case anymore because while many women with PCOS have persistently elevated LH levels throughout their entire cycle, it's not uncommon for some women with PCOS to have normal hormone values.

Still, women with PCOS typically will have FSH levels that are lower than the LH level, so, again, this test can support a diagnosis of PCOS, but not confirm it.

Also, if your FSH is elevated, it can be an indication of a condition called premature ovarian insufficiency.

DHEA/Testosterone Blood Test

Dehydroepiandrosterone (DHEA) and testosterone are two of the androgens or male hormones. These androgens are responsible for many of the male secondary sex characteristics like abnormal hair growth or loss and acne, which explains the symptoms that PCOS sufferers experience. Androgens also cause menstrual irregularities in women.

While elevation of testosterone is typical in women with PCOS, it's important to note that you can have signs of high androgen levels like acne and hair growth, but have normal androgen levels on your blood test—and still have PCOS. In other words, a doctor has to put together your physical exam with your labs to make the diagnosis.

Rarely, a very high testosterone level could be a sign of an androgen-secreting tumor of the ovary. Likewise, high DHEA levels could be a sign of an androgen-secreting tumor of the adrenal glands (small glands that sit upon your kidneys).

17-Hydroxyprogesterone Blood Test

This blood test is used to determine the presence of late-onset congenital adrenal hyperplasia, another medical condition that can mimic the symptoms of PCOS.

Thyroid Function Blood Tests

These tests are used to rule out thyroid dysfunction as a cause of your menstrual irregularity. Thyroid stimulating hormone (TSH) is also secreted by the pituitary gland and controls the release of the two thyroid hormones, T3 and T4. These two hormones control basic metabolism and could produce menstrual changes similar to those in PCOS. Either higher or lower than normal lab values could indicate thyroid disease and should be followed up.

Prolactin Blood Test

Secreted by the pituitary, prolactin is a hormone whose primary responsibility is promoting lactation in women. Elevated values can cause a lack of menstruation. If your level is elevated, your doctor will test your thyroid if he or she hasn't already since untreated hypothyroidism can cause an elevated prolactin level. In addition, your doctor will order an MRI of the pituitary gland to evaluate for a tumor called a prolactinoma.

Blood Tests When Diagnosed With PCOS

If your doctor diagnoses you with PCOS, he or she will want to evaluate you for type 2 diabetes and high cholesterol levels, which are common metabolic abnormalities in women with PCOS. These tests include:

  •  Glucose tolerance test (GTT): This test will allow your physician to measure your response to a sugar stimulus. Insulin is the major hormone that deals with sugar and fuel within your body. The examiner will give you a very sweet, sugary solution to drink. Blood tests will be drawn before the test begins and at one and two hours afterwards. Urine samples may be collected as well to measure the glucose in your urine. It's important to not eat or drink anything once the test begins, or for 12 hours before, as it will affect the results. Normally, blood sugar should return to normal within two hours. If your blood sugar levels are elevated beyond the test, it may indicate that your body doesn't respond as quickly to insulin, indicating a diagnosis of prediabetes or diabetes. Your doctor may confirm this abnormal finding by repeating the test.

  • Cholesterol test: This test is sometimes referred to as a lipid panel. Women with PCOS can have high cholesterol. Because of the association of PCOS with metabolic disturbances, including heart disease and diabetes, it's important to monitor your cholesterol and blood pressure. This will allow your practitioner to quickly treat you if you develop risk factors for cardiac disease and minimize their effects.

Bottom Line

While it may seem like your doctor is ordering a number of blood tests, don't be alarmed. This is common protocol and is done to ensure that the right diagnosis is made so you can move forward with the appropriate care and treatment. 

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