The thyroid is a small, yet powerful gland in the neck that releases hormones that help regulate many of the body's functions. One of those hormones is thyroxine, which is necessary for the heart, brain, and other organ systems to function properly.
While thyroid disease can lead to a variety of potentially serious symptoms, including fatigue, anxiety, palpitations, forgetfulness, high blood pressure, and fluctuations in weight, it’s fairly simple to diagnose.
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Thyroid Disease: Blood Tests
There are many different causes of thyroid disease, but they all lead to one of two issues regarding thyroid function. The thyroid either produces too much hormone (hyperthyroidism), or too little (hypothyroidism). Under normal circumstances, the pituitary gland in the brain tells the thyroid how much hormone it should release. But sometimes infections, medications, and even the body's own immune system can interrupt communication between the pituitary and the thyroid. When this happens, thyroid function becomes altered.
Fortunately, a simple blood test can provide important information about several hormones related to thyroid function, including:
  • TSH. Thyroid-stimulating hormone (TSH) is what the pituitary gland releases to tell the thyroid when to produce thyroid hormones. A low level of TSH in the blood usually means that thyroid function is excessive (hyperthyroidism), while a high level of TSH generally indicates that too little thyroid hormone is being produced (hypothyroidism).
  • T4 (thyroxine). An excess of T4 in the blood is indicative of an overactive thyroid, whereas low levels of T4 indicate underactive thyroid function. Testing T4 blood levels also helps doctors pinpoint whether or not thyroid disease is due to a problem in the pituitary gland or the thyroid gland itself.
  • T3 (triiodothyronine). T3 is another important thyroid hormone. T3 levels can fluctuate quite a bit, but high levels of T3 are typically due to hyperthyroidism, while low levels are caused by hypothyroidism.
  • Thyroid antibody. Autoimmune thyroid diseases (like Hashimoto's thyroiditis or Graves' disease) cause the immune system to release proteins called antibodies that attack the thyroid as if it were foreign tissue. Blood tests can reveal the presence of thyroid antibodies and allow doctors to diagnose such an autoimmune disease. Thyroid Disease: The First Steps to Diagnosis
    If your doctor suspects that you have thyroid disease, he or she will order blood tests. The blood draw itself only takes a few minutes, but you'll have to wait up to a week for the test results. Your doctor will probably schedule another visit or a phone call to discuss these results with you and give you a chance to ask any questions.
    If your blood tests indicate that you have a thyroid problem, but don't provide enough information for a clear diagnosis, you may need additional thyroid tests.
    Thyroid Disease: Other Tests
    Other tests that can help diagnose thyroid disease include:
    • Radioactive iodine uptake (RAIU). The thyroid gland uses iodine in the blood to make thyroid hormones. Swallowing a small, radioactive iodine pill helps doctors measure how much iodine your thyroid gland uses. If the thyroid gland draws upon a lot of the iodine released by the pill (leading to a high RAIU reading), hyperthyroidism is probably the cause. A low RAIU usually reflects an underactive thyroid.
    • Thyroid scan. Often used along with RAIU, a thyroid scan can reveal specific regions in the thyroid that are using either too much or too little radioactive iodine. This scan can help doctors decide whether a thyroid biopsy is necessary to confirm the diagnosis.
    • Ultrasound. Ultrasound images of the thyroid can show underlying structural causes of thyroid disease such as a tumor or cyst.
    Diagnosing thyroid disease, determining the cause, and starting treatment can help prevent serious health complications like heart disease and mental health problems. Thyroid tests are easily done and relatively painless, usually only requiring a blood sample or imaging test. Once properly diagnosed, thyroid disease symptoms can generally be managed effectively.