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Thyroid hormones
TSH
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Thyroid stimulating hormone (TSH) is produced in the pituitary gland in order to regulate the production of thyroid hormones thyroxine (T4) and triiodothyronine (T3) by the thyroid gland. If thyroid hormones in the blood are low, then more TSH is produced to stimulate the thyroid gland to produce more of them. If thyroid hormone levels are high, then the pituitary produces less TSH to slow the production of thyroid hormones. If TSH is too high or too low, it normally signifies that there is a problem with the thyroid gland which is causing it to under or over produce thyroid hormones. Sometimes a disorder of the pituitary gland can also cause abnormal TSH levels.
Free thyroxine
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Thyroxine (T4) is one of two hormones produced by the thyroid gland. It works to speed up the rate of your metabolism. Most T4 is bound to carrier proteins in the blood - it is only the free, or unbound, T4 that is active in the body, which is measured in this test. Free T4 is the less active of the two main thyroid hormones. To have an impact on your cells it needs to convert to the more active T3 when your body needs it.
Special instructions
How to prepare for your test
Prepare for your Underactive Thyroid Levothyroxine Monitoring Blood Test by following these instructions. Please take your sample before 10am. Do not take biotin supplements for two days before this test, discuss this with your doctor if it is prescribed.
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FAQs
What is in an underactive thyroid monitoring test?
This test measures TSH and free thyroxine (FT4) to assess your underactive thyroid medication.
How do I take my test?
Once you've ordered your test and the sample collection kit has been delivered to your home, follow the easy instructions to collect your sample and post it back to the lab in the envelope provided. You will then receive your results on your online portal with doctor's recommendations, making it easy to monitor any changes in your results over time. You can also download your results as a PDF to share with your GP. You may want to let your GP know you are having these tests done to help with your treatment schedule.
What is an Underactive Thyroid Levothyroxine Monitoring Blood Test?
Our Underactive Thyroid Levothyroxine Monitoring Blood Test includes the routine markers you would typically get from your GP to test if you have an underactive thyroid (hypothyroidism) and take levothyroxine.