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"What does a TSH test measure?"

ZocdocAnswersWhat does a TSH test measure?


My doctor will perform a TSH test because he thinks something is wrong with my thyroid. What will the test look for?


TSH is a blood test that measures the activity of your thyroid gland. Your primary care physician can discuss thyroid disorders with your in further detail and which symptoms you have that might be characteristic of a thyroid abnormality. The thyroid gland produces a hormone thyroxine, T4, which is converted to T3 and is important in metabolism and development. The hypothalamus (a structure in your brain) produces TSH (Thyroid Stimulating Hormone) which stimulates the thyroid gland to produce thyroxine. When these thyroid hormone levels are abnormal, a patient can develop hypothyroidism (low thyroid level) or hyperthyroidism (high thyroid level.) In testing for abnormal thyroid activity, a TSH level is often obtained as a screening test. However, if that is even slightly abnormal, other testing if often required including T4 and T3 levels and occasionally other hormone levels. Symptoms of hyperthyroidism include heat intolerance, weight loss, increased appetite, heart palpitations and tremors. TSH in a patient with hyperthyroidism will be low and T4 will be high. Symptoms of hypothyroidism include fatigue, weight gain, constipation, headache, coarse skin, and cold intolerance. If a patient has hypothyroidism, TSH will be high and T4 will be low. You should follow up with your primary care physician to discuss your symptoms, need for thyroid testing, and labwork results. If there is concern for thyroid abnormalities after testing, a consultation with an endocrinologist should be considered.

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