Thyroid gland how does it work

The pituitary affects the thyroid gland by producing a hormone called thyroid-stimulating hormone TSH , which prompts the thyroid to release more T4 and T3. If there is too much T4 circulating in the blood, the pituitary reduces the amount of TSH produced, which then causes thyroid activity to slow. If there is too little T4, the pituitary increases the amount of TSH. In this way, T4 and T3 levels in the blood are kept relatively constant.

The pituitary gland, in turn, is overseen by a part of the brain called the hypothalamus. A shortage of iodine in the diet is a common cause of goitre, especially in areas where the soil has little iodine. In attempting to make more thyroid hormone, the gland gets larger and larger. This is also common with underactive thyroids, as the pituitary attempts to speed them up.

Overactive thyroids can also produce goitres because their overactivity is often due to overstimulation. Goitres indicate a problem with the thyroid or iodine intake. An overactive thyroid releases too much T4 and T3 into the bloodstream, causing the metabolism to speed up too much. This is an autoimmune condition in which antibodies behave like TSH and stimulate the thyroid uncontrollably. Complications of untreated hyperthyroidism include liver damage and heart failure, which can lead to death.

Symptoms of an overactive thyroid include:. An underactive thyroid releases too little T4 and T3 into the bloodstream, causing the metabolism to slow down too much. This is an autoimmune condition in which white blood cells and antibodies attack the thyroid gland. If not treated, the metabolism will continue to slow and will ultimately in 10 to 15 years lead to death.

Symptoms include:. When these symptoms increase, the condition may be called myxoedema. Congenital hypothyroidism must be urgently treated to avoid serious brain damage. All newborn babies are now screened for this condition. Problems with thyroid hormone levels can be diagnosed with a simple blood test. Underactivity is treated by taking thyroxine tablets - a form of hormone replacement.

Overactivity is treated with drugs that slow the activity of the thyroid gland. If these do not work, part or all of the thyroid can be removed surgically, or some or all of the active thyroid cells can be killed with radioactive iodine. Nodules and cancers are diagnosed with a variety of different tests, including ultrasound, special x-rays and fine needle biopsies. Hot nodules will generally be removed surgically or destroyed with radioactive iodine.

The hypothalamus releases thyrotropin-releasing hormone TRH , which stimulates the pituitary gland to release thyroid-stimulating hormone TSH. When the hypothalamus and pituitary are working normally, they sense when:. See a picture of thyroid hormone production. Author: Healthwise Staff. This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information.

Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.

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. The pituitary is an endocrine gland located at the base of your brain that controls your endocrine system, including your thyroid. The pituitary affects the thyroid by producing a hormone called thyroid stimulating hormone TSH.

If there is too much T4 in your bloodstream your pituitary produces less TSH, which causes your thyroid activity to slow. If there is not enough T4 hormone the pituitary increases the amount of TSH to help speed up your metabolism. A goitre is when your thyroid gland becomes significantly swollen and enlarged — this can happen if your diet is low in iodine. If you are iodine deficient your pituitary gland may try to compensate by overstimulating your thyroid to produce more thyroid hormone.

When this happens your thyroid grows larger and larger. The presence of goitre in your neck suggests your thyroid is not functioning properly or you are iodine deficient. Hyperthyroidism is a condition where your thyroid is overactive and releases too many T4 and T3 hormones into your bloodstream, creating a hormonal imbalance and causing your metabolism to speed up.

Hypothyroidism is a condition where your thyroid is underactive and releases too little T4 and T3 hormones into your bloodstream. This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional.

Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions. Skip to navigation Skip to main content Site map Accessibility Contact us. Search this site Search all sites Search. Go to whole of WA Government Search.