How does tsh work

It sits behind the bridge of the nose at the base of the brain, close to the optic nerves. This gland works closely with the hypothalamus, a region in the brain.

Editorial Sources and Fact-Checking. TSH test; MedlinePlus. What is the Pituitary Gland? The Pituitary Foundation. How does the thyroid work? PubMed Health. Thyroid disease; Office on Women's Health. T3 and T4 help control your body's metabolism.

Triiodothyronine T3 and thyroxine T4 are needed for normal growth of the brain, especially during the first 3 years of life. A baby whose thyroid gland does not make enough thyroid hormone congenital hypothyroidism may, in severe cases, have below-average intelligence.

Older children also need thyroid hormones to grow and develop normally. A test for thyroid-stimulating hormone TSH is done to:. When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch. There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site. Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test.

The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you. To learn more about Healthwise, visit Healthwise.

Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. Updated visitor guidelines. Top of the page. Thyroid Hormone Production and Function. Topic Overview The thyroid gland uses iodine from food to make two thyroid hormones: triiodothyronine T3 and thyroxine T4. When the hypothalamus and pituitary are working normally, they sense when: Thyroid hormone levels are low, so they secrete more TRH and TSH, which stimulates the thyroid to make more hormones.

Thyroid hormone levels are too high, so they secrete less TRH and TSH, which reduces hormone production by the thyroid. These hormones have a negative effect on the pituitary gland and stop the production of thyroid stimulating hormone if the levels of thyroxine and triiodothyronine are too high. They also switch off production of a hormone called thyrotropin-releasing hormone.

This hormone is produced by the hypothalamus and it also stimulates the pituitary gland to make thyroid stimulating hormone. A simple blood test can measure thyroid stimulating hormone in the circulation. If a person has too much, this may indicate that their thyroid gland is not making enough thyroid hormone, that is, they have an underactive thyroid gland or hypothyroidism.

People with an underactive thyroid often feel lethargic, experience weight gain and feel the cold. Their thyroid gland may enlarge to produce a goitre. Treatment is medication in the form of tablets to bring the level of thyroid hormones back to normal. This also reduces the amount of thyroid stimulating hormone in circulation. It is particularly important for pregnant women to have the correct amounts of thyroid stimulating hormone and thyroid hormones to ensure the healthy development of their babies.