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  • Your thyroid gland (in your neck) produces a hormone called thyroxine (aka T4). Your pituitary gland (in your head, just underneath your brain produces a hormone called thyroid-stimulating hormone (aka TSH). Sometimes a person’s thyroid stops working, so the level of T4 in the blood falls, because it is not secreting enough. When this happens, the pituitary gland releases lots of TSH to ‘nag’ the thyroid – to try and encourage it to make more T4. So if a doctor does a blood test and sees low T4 with high TSH, they think “oh, the thyroid is not working”.

    In your case, it seems like the doctor saw low T4 and also normal or low TSH. So he/she is wondering – if the T4 is low, why isn’t the pituitary responding by releasing more TSH? Could there be something wrong with the pituitary, instead of the thyroid? Perhaps the thyroid is fine and the pituitary has stopped stimulating it. So your doc has ordered a scan to look at the pituitary. I’m guessing you’ll have to have some more blood tests to look for other hormones that the pituitary should be making.

    This doesn’t automatically mean there is definitely something wrong with the pituitary – a lot of people have slightly odd thyroid test results and it means nothing. Genuine pituitary problems are rare, but they often get missed, so doctors are a bit jumpy when there is even a slight suspicion of it.

  • The thyroid gland is under the control of the pituitary gland, a small gland the size of a peanut at the base of the brain (shown here in orange). When the level of thyroid hormones (T3 & T4) drops too low, the pituitary gland produces Thyroid Stimulating Hormone (TSH) which stimulates the thyroid gland to produce more hormones. Under the influence of TSH, the thyroid will manufacture and secrete T3 and T4 thereby raising their blood levels. The pituitary senses this and responds by decreasing its TSH production. One can imagine the thyroid gland as a furnace and the pituitary gland as the thermostat. Thyroid hormones are like heat. When the heat gets back to the thermostat, it turns the thermostat off. As the room cools (the thyroid hormone levels drop), the thermostat turns back on (TSH increases) and the furnace produces more heat (thyroid hormones)

    best of luck

  • the thyroid and pituitary are two glands that release hormones. if something is wrong with your thyroid then the doctor may want to check similar organs to make sure they are healthy as well.

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