Platform
Company
Immunology & Autoimmune
Review status
Currently under review
Pending specialist review and validation.
Thyroid stimulating hormone is a signal made by your pituitary gland that tells your thyroid how much thyroid hormone to produce. The thyroid then releases thyroxine and triiodothyronine, which help regulate energy use, body temperature, heart function, digestion, and mood.
A TSH test measures the amount of this pituitary signal in your blood. Because the pituitary adjusts TSH in response to circulating thyroid hormone, TSH is a sensitive indicator of how your thyroid system is working. It is commonly tested on its own or together with free T4 and sometimes free T3.
TSH helps your care team assess for an underactive thyroid, an overactive thyroid, or issues with pituitary function. It is often ordered when you have symptoms such as fatigue, weight change, sensitivity to cold or heat, palpitations, hair or skin changes, mood changes, or menstrual irregularities. It is also used to monitor treatment if you are taking thyroid medication or have had thyroid surgery or radioiodine.
Your clinician may check TSH during pregnancy planning or early pregnancy, in the presence of autoimmune thyroid conditions such as Hashimoto thyroiditis or Graves disease, and when other illnesses or medications could affect thyroid function. Understanding your TSH in context helps guide safe and timely follow up.
Higher-than-expected TSH usually suggests your thyroid is not making enough hormone, while lower-than-expected TSH often suggests your thyroid is making too much. However, results must be interpreted alongside your symptoms, exam, and other tests such as free T4, free T3, and thyroid antibody tests. In rare cases, pituitary or hypothalamic conditions can lead to results that do not follow the usual patterns.
If your result is outside the expected range, your clinician may repeat the test, review your medications and supplements, and order additional labs or imaging. Illness, pregnancy, and recent changes in thyroid medication can temporarily shift TSH. Do not change or stop medications without medical advice. If you develop severe symptoms such as chest pain, shortness of breath, or confusion, seek urgent care.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
TSH follows a daily rhythm, tending to be higher at night and lower later in the morning. Severe or recent illness can temporarily alter TSH, so your clinician may repeat testing after recovery for a clearer picture.
High-dose biotin supplements and certain antibodies in the blood can interfere with some immunoassays, making TSH appear falsely high or low. Tell your care team about supplements; you may be asked to pause biotin before testing.
Levothyroxine timing, antithyroid drugs, amiodarone, lithium, glucocorticoids, dopamine agonists, and opioids can shift TSH results. Take thyroid medication consistently as instructed and report all medicines to avoid misinterpretation.
Pregnancy alters thyroid physiology and pituitary signaling. Different clinical targets are used during pregnancy, and additional tests may be recommended. Postpartum changes can also affect TSH temporarily.
Conditions affecting the pituitary or hypothalamus can lead to inappropriately normal or low TSH despite abnormal thyroid hormone levels. Your clinician may use free T4 and imaging if central causes are suspected.
Very high or very low iodine intake, and recent iodinated contrast for imaging, can transiently alter thyroid function and TSH. Share recent procedures and diet changes with your clinician.
References