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Top of the page. There is a third actor involved in this communication. The pituitary gland responds either directly to the thyroid hormones in the blood, but it also responds to signals from the hypothalamus , which sits above the pituitary gland as part of your brain.
The hypothalamus releases its own hormone thyrotropin-releasing hormone TRH. The thyroid gland produces thyroxine referred to as T4 , which is a relatively inactive prohormone. The highly active hormone is triiodothyronine referred to as T3. Collectively, thyroxine and triiodothyronine are referred to as the thyroid hormones. Once secreted by the thyroid, specific enzymes in other tissues like the liver or kidneys may transform T4 in to the active hormone T3.
In addition, there are other hormone-producing cells within the thyroid gland called C-cells. These cells produce calcitonin. Calcitonin plays a role in regulating calcium and phosphate levels in the blood, which is important for your bone health and maintenance. As described earlier, hormones secreted by the pituitary gland TSH stay constant in your blood circulation, but their levels may increase or decrease when T4 levels in the blood are changing.
This hypothalamic-pituitary-thyroid feedback loop keeps the levels of T4 in your blood stable and reacts to small changes immediately. However, there are several disorders associated with the thyroid gland with most problems concerning the production of thyroid hormones.
Either the thyroid gland produces too much hormone called hyperthyroidism or your thyroid doesn't produce enough hormone called hypothyroidism , resulting in your body using energy faster or slower than it should.
Symptoms for hypothyroidism is the contrary of hyperthyroidism such as weight gain, slower heart rate, fatigue, more frequent and stronger menstrual periods, forgetfulness, dry skin and hair, hoarse voice and intolerance to cold. In addition, hypothyroidism is often accompanied by an enlargement of the thyroid gland known as goitre. On a worldwide scale, approximately million people have some form of thyroid disease.
People of all ages and races can get thyroid disease. Skip to main content. Endocrine System. Search for:. The Thyroid Gland. Learning Objectives Summarize the anatomy and purpose of the thyroid gland. 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. When the pituitary gland detects that thyroid hormone levels are too low, it secretes more TSH.
If the pituitary gland detects too much thyroid hormone, it releases less TSH. Author: Healthwise Staff. Kim MD - Endocrinology. This information does not replace the advice of a doctor.
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