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"Why would a doctor order a thyroid test?"

ZocdocAnswersWhy would a doctor order a thyroid test?


My doctor ordered a thyroid test but didn't really say why or what it will mean when we get the results. I went to the doctor because I thought I had mono because I am tired all of the time. What do you think my doctor is looking for?


I am sorry that you have been feeling tired. It is likely that your physician was testing for hypothyroidism which can cause increased fatigue. You should follow up with your primary care physician regarding the meaning of the test results and if further evaluation is required. The thyroid gland produces a hormone thyroxine, T4 which is converted to T3, which is important in metabolism and development. The pituitary gland produces TSH (thyroid stimulating hormone) which stimulates the thyroid to produce thyroxine. When these thyroid hormone levels are abnormal, then a patient can develop hypothyroidism (low thyroid level) or hyperthyroidism (high thyroid level). In testing for thyroid activity, a TSH level is often obtained as a screening test. However, if that is even slightly abnormal, other testing is often required including T4 and T3 levels. Symptoms of hyperthyroidism include heat intolerance, weight loss, increased appetite, anxiety, heart palpitation and tremor. In this case, TSH will be low and T4 will be high. Symptoms of hypothyroidism include fatigue, weight gain, constipation, headache, coarse skin, menstrual disturbances, and cold intolerance. This is likely what your physician is testing for given your history of chronic fatigue. If a patient has hypothyroidism, TSH will be high and T4 will be low. Treatment of hypothyroidism is thyroid supplementation. You should see your primary care physician to discuss changes in your symptoms, test results, and possible further evaluation.

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