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What Affects TSH Tests?

The TSH test is a common laboratory test used by physicians to check for levels of thyroid-stimulating hormone (TSH) in the bloodstream. The TSH test results are an important component of a comprehensive diagnosis for thyroid conditions. The test results can, however, be influenced by some medications, stressful situations or other illnesses. By being knowledgeable about these influences, patients can better prepare for the TSH test and help doctors ensure the test results are accurate.

  1. TSH Test

    • As a diagnostic tool, the TSH test is used to look for evidence of an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism). The test is also used as a way to monitor how the body is responding to medications given for thyroid treatment or as a follow-up to radiation therapy or surgery. Newborns suspected to have hypothyroidism are typically given a TSH test to confirm this diagnosis.

    Medications

    • Several medications can affect the results of a TSH test. Corticosteroids are medicines which are very similar to the body's natural hormones and can cause incorrect TSH test results. Brand names of corticosteroids include Cortisone, Deltasone and Celestone. Antipsychotic medications such as lithium also influence TSH test results. Brand names include Lithobid, Eskalith and Lithotabs. Heparin, a drug used as a blood thinner, also can create incorrect test results.

    Tests or Treatments

    • Diagnostic tests or treatments, such as X-rays that include an iodine dye, influence TSH tests. Iodine interacts with the thyroid and affects its ability to produce the T4 and T3 hormones. Introduction of extra iodine into the body can cause invalid TSH test results. Additionally, diagnostic tests that use radioactive substances will affect a TSH test. Be sure your doctor is aware of any such tests or treatments recently received.

    Psychological and Illness

    • The endocrine system is sensitive to emotional and physical stress. Severe emotional stress, especially when it is long term, puts extra demands on the endocrine system and may change the normal output of the body's hormones. Factors such as lack of proper sleep, poor nutrition and chronic, long-term illness also affect hormonal levels and influence TSH test results.

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