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Going to the Doctor: Understanding Your Blood Tests


Updated June 09, 2014

Laboratory technician holding test tubes containing blood samples
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Question: Going to the Doctor: Understanding Your Blood Tests
Many times, when the doctor is considering diagnosing PCOS, blood tests will be used to examine various hormonal levels. Here is a list of the most common blood tests that may be run.
  • FSH/LH
    Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) are produced by the pituitary in response to the presence of another hormone. FSH stimulates the growth of an egg follicle within the ovary, while the surge of LH triggers the release of the egg during ovulation. Both typically ‘surge’, elevating lab values, just prior to ovulation. Previous diagnoses were made based on a LH to FSH ratio of greater then 3:1. This is not the case anymore because while many women with PCOS have persistently elevated LH levels throughout their entire cycle, it is not uncommon for women to have normal hormone values. If FSH is elevated, it can be an indication of decreased ovarian reserve, or aging/menopause.

  • DHEA/Testosterone
    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. They also cause menstrual irregularities in women. Elevations of testosterone is typical in women with PCOS. A high DHEA level would indicate an adrenal cause, like Congenital Adrenal Hyperplasia or an adrenocortical tumor, for the patient’s symptoms.

  • Thyroid function
    These tests are used to rule out thyroid dysfunction as a cause of menstrual irregularity. Thyroid Stimulating Hormone (TSH) is also secreted by the pituitary 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 then normal lab values could indicate thyroid disease and should be followed up.

  • Prolactin
    Secreted by the pituitary, this hormone’s primary responsibility is promoting lactation in women. Elevated values can cause amenorrhea, so this test is usually performed to look for another source of the symptoms. If elevated, your doctor will order more tests (usually an MRI or other blood tests) to figure out why it is high.

  • Glucose Tolerance Test (GTT)
    This test will allow your physician to measure your response to a sugar stimulus. Insulin is the major hormone which deals with sugar and fuel within the body. The examiner will give you a very sweet, sugary solution to drink. Blood tests will be drawn before the test begins, a onr hour after you drink the solution, and again at two and three hours afterwards. Urine samples may be collected as well to measure glucose in the urine. It is 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 3 hours. If blood sugar levels are elevated beyond the test, it may indicate that your body does not respond as quickly to insulin. putting you at risk for developing diabetes.

  • Cholesterol
    Women with PCOS can have high cholesterol. Because of the association of PCOS with metabolic disturbances, including heart disease and diabetes, it is 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.
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