Blood Tests for PCOS

Blood tests for polycystic ovary syndrome (PCOS) measure pituitary, adrenal, and thyroid hormones, cholesterol, and blood sugar. These tests rule out other conditions that cause similar symptoms as PCOS.

PCOS blood tests include follicle-stimulating hormone (FSH), progesterone, testosterone, and prolactin. These tests cannot confirm a PCOS diagnosis on their own. An ultrasound showing multiple ovarian cysts is the main diagnostic feature of PCOS.

This article discusses PCOS blood tests. It explains the different hormone levels and what they may mean. It also details other conditions that must be excluded before your healthcare provider can diagnose PCOS.

Pregnancy Test

If you've missed your period or have stopped menstruating, the first test your healthcare provider will likely do is a pregnancy test.

Like versions that use a urine sample, a pregnancy blood test looks for human chorionic gonadotropin (hCG), a hormone that is only present if you are pregnant.

If the pregnancy test is negative, your provider will move forward with other blood tests.

FSH/LH Blood Test

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are made by the pituitary gland, a pea-sized organ 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. 

A diagnosis of PCOS used to be made based on an LH-to-FSH ratio greater than 3-to-1 (3:1), but this is no longer the case. Many people with PCOS have persistently elevated LH levels throughout their menstrual cycles and otherwise normal hormone levels.

If your FSH is elevated, it could also indicate an unrelated condition called primary ovarian insufficiency.

17-Hydroxyprogesterone Test

The 17-hydroxyprogesterone blood test (17-OHP) detects a hormone made by the adrenal glands. It is involved in the production of the stress hormone cortisol.

The 17-OHP test is used to determine the presence of late-onset congenital adrenal hyperplasia, another medical condition that can mimic the symptoms of PCOS.

DHEA/Testosterone Blood Test

Dehydroepiandrosterone (DHEA) and testosterone are hormones called androgens. These hormones are responsible for secondary male sex characteristics and are the cause of many of the symptoms of PCOS, including acne, hirsutism (hair growth on the face, chest, and back), female-pattern baldness, and menstrual irregularities.

An elevation of testosterone is typical in people with PCOS, but it is possible to have a spontaneous outbreak of acne and hirsutism with normal androgen levels and still be diagnosed with PCOS.

Androgen irregularities are a guide to help diagnose PCOS, but they are not a smoking gun.

Other androgens your healthcare provider may test when evaluating PCOS include:

• Androstenediol (A5), which is used to make the sex hormones estrogen and testosterone
• Androstenedione (A4), which is used to make estrogen and testosterone
• Androsterone, a byproduct of testosterone breaking down
• Dihydrotestosterone (DHT), a byproduct of testosterone
  

Thyroid Function Tests

A thyroid function panel of blood tests is used to rule out thyroid dysfunction as the cause of your menstrual irregularities.

Thyroid-stimulating hormone (TSH) is also secreted by the pituitary gland and regulates the release of the two thyroid hormones: triiodothyronine (T3) and thyroxine (T4).

These two hormones regulate basic metabolic functions. Having low levels of either could cause menstrual changes similar to those experienced in people with PCOS.

Sex Hormone-Binding Globulin (SHBG) Test

Sex hormone-binding globulin (SHBG) is a carrier protein in the blood that transports androgens and estrogen. A low SHBG level is a sign of PCOS.

Low SHBG is also associated with common co-morbidities of PCOS, including:

• Abnormal glucose metabolism
• Abnormal lipid metabolism
• Hyperandrogenemia
• Insulin resistance
• Obesity
  

In addition, alterations in specific genes that regulate SHBG are associated with a higher risk of PCOS. 

Anti-Mullerian Hormone (AMH) Test 

High levels of anti-Mullerian hormone (AMH) are another sign of PCOS. AMH is released from immature antral follicles in the ovaries, the small fluid-filled cyst-like structures that are a key feature of PCOS. 

AMH is believed to inhibit a follicle’s ability to mature into an egg (oocyte). This can prevent ovulation, cause longer menstrual cycles, and lead to infertility.

Estrogen Levels Test

Abnormal estrogen levels are also common with PCOS. Estrogen can be high or low with PCOS, though often estrogen level tests come back normal.

Estrogen is the star hormone of the female reproductive system. Its levels rise and fall throughout the cycle. When estrogen levels are high, it prompts the release of other hormones that stimulate ovulation. If pregnancy does not occur, estrogen levels drop, prompting menstruation.

Estrogen works in tandem with progesterone and other hormones to regulate the menstrual cycle. Both low and high estrogen levels can contribute to longer menstrual cycles, a common symptom of PCOS.

High estrogen levels are linked to estrogen dominance, a hormone imbalance associated with irregular menstrual cycles. In women with PCOS, high estrogen levels are believed to be caused by the conversion of insulin and testosterone into estradiol, a form of estrogen.

Prolactin Test

Prolactin is a hormone made by the pituitary gland. Its primary role is promoting lactation. Elevated values of this hormone (hyperprolactinemia) can cause irregular menstruation (oligomenorrhea) or a total lack of menstruation, known as amenorrhea.

If your prolactin levels are elevated, your provider will test your thyroid function because untreated hypothyroidism can also cause elevated prolactin.

Your provider may also want you to have a magnetic resonance imaging (MRI) scan of your pituitary gland to rule out a tumor called a prolactinoma.

Testing for PCOS-Related Conditions

If you are diagnosed with PCOS, your provider will also screen you for type 2 diabetes and high cholesterol—two conditions that are common in people with PCOS.

Oral Glucose Tolerance Test

An oral glucose tolerance test (OGTT) measures your response to sugar. Insulin is the major hormone that regulates blood sugar (glucose) and how it's metabolized for energy.

For the OGTT, you'll first have a blood sample taken so that your starting blood sugar level is recorded. Then you will be asked to drink a sugary solution. Blood will be drawn again two hours later to see how well your body is clearing the glucose you ingested.

In people without diabetes, blood sugar levels should return to normal within two hours of drinking the solution. If not, the test can be indicative of prediabetes or diabetes.

Urine samples are sometimes collected as well.

Lipid Panel

A lipid panel measures all of the key values associated with high cholesterol, including total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and another type of lipid called triglycerides.

People with PCOS often have high cholesterol, which can increase their risk of heart disease and diabetes.

When Are PCOS Blood Tests Taken?

PCOS blood tests may need to be repeated at different times of the month. Hormone levels rise and fall throughout the menstrual cycle. The optimal time to check these levels varies by hormone, as follows:

• Estrogen and FSH levels are typically measured around day three of your menstrual cycle. (Day one is the day you start your period.)
• LH levels are often checked mid-cycle, just before ovulation.
• Progesterone levels are typically measured post-ovulation, in the week before your expected period.

However, since women with PCOS have irregular menstrual cycles, this can be tricky. Your healthcare provider may wait for you to get your period to start these tests or take them at random times in your cycle.

Hormone testing does not typically require fasting. However, if cholesterol or glucose are being tested at the same time, you may need to stop eating for at least eight hours before the test.

The initial blood draw should only take a few minutes. The amount of time it takes to get PCOS blood test results depends on the lab. Results can be ready within hours but may take a few days if the lab is very busy.

Summary

There is no single test that can diagnose PCOS. Instead, a provider needs to rule out other medical conditions that cause similar symptoms, and blood tests are just one part of this process.

PCOS blood tests measure hormone levels, including 17-OHP, AMH, DHEA, estrogen, FSH, hCG, LH, prolactin, SHBG, testosterone, T3, T4, and TSH,

When a person is diagnosed with PCOS, they also need to be tested for other conditions that are very common in people with the disease, such as diabetes and high cholesterol.