Thyroxine (T4) Free Plus TSH

Why is this test important? Thyroxine (T4) Free is one of two major hormones produced by the thyroid gland, and it accounts for nearly 90 percent of the all thyroid hormone in your system. This test measures the level of free (not total) T4 hormone in your body. This is an important distinction, since the level of free T4 hormone illustrates how much is immediately available for uptake and use by cells. In addition, this test also measures the level of thyroid-stimulating hormone (TSH) produced by the pituitary gland. The resulting TSH level will indicate if your body is producing too much—or too little—of this critical hormone.

What does the test include? The HealthCheckUSA thyroxine (T4) free plus TSH test involves a simple blood sample taken by a qualified technician. Because this test includes a TSH screening, remember that medications like corticosteroids, aspirin and lithium can interfere with those results. Also, if you've had a recent X-ray that used iodine dye—or other radioactive tests—ask your doctor when you can take an accurate TSH test. Pregnant women in their first trimester should also ask their doctor about the proper time to get a TSH test. The blood tests will be analyzed by an accredited laboratory, and you can access the confidential results on the HealthCheckUSA web site within four business days after testing.

Who should be tested? People with a family history of thyroid problems should strongly consider testing. This is even more important if you're pregnant or just had a baby, since proper T4 (and T3) levels are essential to brain development in the early years of a child's life. Additionally, consider testing if you are experiencing symptoms of hypothyroidism (unusual weight gain, lethargy, dry skin, a constant feeling of cold, or constipation) or hyperthyroidism (sudden weight loss, increased heart rate, recurring warm or sweaty feeling, or diarrhea).