Q: Is the TSH (thyroid stimulating hormone) a good way to titrate my thyroid hormone therapy?
A: Yes, absolutely! Once you have been diagnosed with hypothyroidism and started on thyroid hormone therapy, the TSH blood test is the best way to monitor your thyroid hormone replacement. TSH is made in the pituitary and the blood levels reflect how your own body is responding to the amount of thyroxine in your blood. When thyroid hormone levels are low, the pituitary gland increases secretion of TSH and indicates that your thyroxine dose should be increased. If your TSH level is low, your thyroid hormone dose is excessive and should be reduced. In most patients on thyroxine replacement, the goal TSH level is between 0.5 to 2.5 mU/L. Patients who have had thyroid cancer are usually on higher doses of thyroxine and their target TSH level is lower than normal. A TSH blood test should be obtained at least every 6-12 months while you are on a stable thyroxine dose, and more often if your dose is changed. Your doctor will usually wait 6-8 weeks after a thyroxine dose adjustment to measure your TSH, when the levels of thyroxine have reached a steady state. If you are on thyroxine and planning a pregnancy, or are currently pregnant, you will need more frequent TSH monitoring and should contact your physician. Although TSH is the best test for most patients on thyroxine replacement, those who have pituitary disease or previous pituitary surgery or radiation, are usually followed with measurement of free thyroxine, rather than a TSH.
Take a look at our Patient Web Brochure Hypothyroidism to learn more about hypothyroidism and how it is treated.
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