Students Teachers Patients Browse. Human body. Home Hormones Triiodothyronine. Triiodothyronine Triiodothyronine is a thyroid hormone that plays vital roles in the body's metabolic rate, heart and digestive functions, muscle control, brain development and function, and the maintenance of bones.
Alternative names for triiodothyronine T3 What is triiodothyronine? How is triiodothyronine controlled? What happens if I have too much triiodothyronine? What happens if I have too little triiodothyronine? Last reviewed: Jun Prev. Vitamin D. Key Takeaways Key Points The thyroid gland controls how quickly the body uses energy, makes proteins, and controls how sensitive the body is to other hormones. It participates in these processes by producing thyroid hormones, the principal ones being triiodothyronine T3 and thyroxine T4.
Hormones released from the thyroid regulate the rate of metabolism and affect the growth and rate of function of many other systems in the body. Hormonal output from the thyroid is regulated by thyroid-stimulating hormone TSH produced by the anterior pituitary, which itself is regulated by thyrotropin-releasing hormone TRH produced by the hypothalamus.
The thyroid gland the thyroid in vertebrate anatomy is one of the largest endocrine glands. Key Terms thyroid-stimulating hormone : Also known as TSH or thyrotropin, this is a hormone that stimulates the thyroid gland to produce thyroxine T4 , and then triiodothyronine T3 , which stimulates the metabolism of almost every tissue in the body.
It is a glycoprotein hormone, synthesized and secreted by thyrotrope cells in the anterior pituitary gland, that regulates the endocrine function of the thyroid gland. Formation, Storage, and Release of Thyroid Hormones Thyroid hormones T4 and T3 are produced by the follicular cells of the thyroid gland and regulated by thyroid-stimulating hormone TSH. Learning Objectives Describe the relationship between thyroxine T4 and triiodothyronine T3.
Thyroxine is believed to be a pro- hormone and a reservoir for the most active and main thyroid hormone T3. Thyroid hormones T4 and T3 are produced by the follicular cells of the thyroid gland and are regulated by thyroid-stimulating hormone secreted by the anterior pituitary gland. Key Terms thyroid-stimulating hormone : A hormone that stimulates the thyroid gland to produce thyroxine T4 , and then triiodothyronine T3 , which stimulates the metabolism of almost every tissue in the body.
Action of Thyroid Hormones The primary function of the thyroid is to produce the hormones triiodothyronine T3 , thyroxine T4 , and calcitonin. Learning Objectives List the actions of thyroid hormones.
Key Takeaways Key Points T4 is converted to T3 by peripheral organs such as the liver, kidney, and spleen.
Triiodothyronine T3 is several times more powerful than T4, which is largely a pro- hormone. The regulation of actin polymerization by T4 is critical to cell migration in neurons and glial cells and is important for brain development. Thyroid hormones play an important role in regulating metabolic rate and body temperature.
Key Terms thyroxine : A hormone an iodine derivative of tyrosine produced by the thyroid gland that regulates cell metabolism and growth. Control of Thyroid Hormone Release The production of thyroxine and triiodothyronine is regulated by thyroid-stimulating hormone TSH that is released from the anterior pituitary.
Learning Objectives Explain how thyroid hormone release is controlled. TSH is secreted by the anterior pituitary gland and is itself under the control of thyrotropin-releasing hormone TRH. TRH is secreted by the hypothalamus. Both TSH and TRH secretion are inhibited when elevated thyroid hormone levels are detected in the blood and provide negative feedback to the hypothalamus and anterior pituitary gland.
Key Terms thyroid-stimulating hormone : A hormone released from the anterior pituitary gland that stimulates the release of thyorid hormones. Licenses and Attributions.
These changes are usually not serious, and most pregnant women don't need T3 testing. But your health care provider may order a T3 test during pregnancy if you have:. The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health. Triiodothyronine T3 Tests. What is a triiodothyronine T3 test? The T3 hormone comes in two forms: Bound T3, which attaches to protein Free T3, which does not attach to anything A test that measures both bound and free T3 is called a total T3 test.
Other names: thyroid function test; total triiodothyronine, free triiodothyronine, FT3. What is it used for? Why do I need a T3 test? You may need a T3 test if you have symptoms of hyperthyroidism. These include: Anxiety Weight loss Tremors in the hands Increased heart rate Bulging of the eyes Trouble sleeping Fatigue Low tolerance for heat More frequent bowel movements.
What happens during a T3 test? Will I need to do anything to prepare for the test? Are there any risks to the test? What do the results mean? If you have questions about your results, talk to your health care provider.
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