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What Organ System Is The Thyroid Gland In

What Does The Thyroid Gland Do

Thyroid, small but vital gland in the body system

The thyroid gland produces hormones that regulate the body’s metabolic rate controlling heart, muscle and digestive function, brain development and bone maintenance. Its correct functioning depends on a good supply of iodine from the diet. Cells producing thyroid hormones are very specialised in extracting and absorbing iodine from the blood and incorporate it into the thyroid hormones.

When Should I Call My Doctor

Some symptoms can point to a serious health condition, such as diabetes. Call your provider if you have:

  • The urge to urinate a lot.
  • Extreme thirst, even after youve had plenty of water.
  • Nausea or stomach pain that doesnt go away.
  • Sudden weight loss or unexplained weight gain.
  • Severe exhaustion or weakness.
  • Problems with sweating too much.
  • Sudden episodes of rapid heart hearts or elevated blood pressure
  • Developmental or growth delays.

Treatment For Thyroid Gland Disorders

Problems with thyroid hormone levels can be diagnosed with a simple blood test. The presence of antibodies in the blood will confirm Graves or Hashimotos disease. 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. Cold nodules are frequently left alone and simply kept under observation. Cancer is treated by surgically removing the thyroid gland, followed by treatment with radioactive iodine to destroy any cells which may have spread.Taking iodine supplements can be dangerous for patients with Graves disease or hot nodules.

Things That Can Go Wrong

Too much or too little of any hormone can be harmful to your body. For example, if the pituitary gland produces too much growth hormone, a teen may grow excessively tall. If it produces too little, a teen may be unusually short. Doctors can often treat problems with the endocrine system by controlling the production of hormones or replacing certain hormones with medication.

Endocrine problems that can affect teens include:

Adrenal insufficiency. This condition occurs when the adrenal glands dont produce enough corticosteroids. The symptoms of adrenal insufficiency may include weakness, fatigue, abdominal pain, nausea, dehydration, and skin changes. Doctors treat adrenal insufficiency with medications to replace corticosteroid hormones.

Type 1 diabetes. When the pancreas fails to produce enough insulin, type 1 diabetes occurs. In kids and teens, type 1 diabetes is usually an autoimmune disorder, which means that some parts of the bodys immune system attack and destroy the cells of the pancreas that produce insulin. To control their blood sugar levels and reduce the risk of developing diabetes problems, kids and teens with this condition need regular injections of insulin.

Reviewed by: Steven Dowshen, MDDate reviewed: March 2012

Note: All information on KidsHealth is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

What Are The Parts Of The Endocrine System

Thyroid System Image Stock Illustration

While many parts of the body make hormones, the major glands that make up the endocrine system are the:

  • hypothalamus
  • the ovaries
  • the testes

The pancreas is part of the endocrine system and the digestive system. That’s because it secretes hormones into the bloodstream, and makes and secretes enzymes into the digestive tract.

Hypothalamus: The hypothalamus is in the lower central part of the brain. It links the endocrine system and nervous system. Nerve cells in the hypothalamus make chemicals that control the release of hormones secreted from the pituitary gland. The hypothalamus gathers information sensed by the brain and sends it to the pituitary. This information influences the hormones that the pituitary makes and releases.

Pituitary: The pituitary gland is at the base of the brain, and is no bigger than a pea. Despite its small size, the pituitary is often called the “master gland.” The hormones it makes control many other endocrine glands.

The pituitary gland makes many hormones, such as:

The pituitary also secretes endorphins , chemicals that act on the nervous system and reduce feelings of pain. The pituitary also secretes hormones that signal the reproductive organs to make sex hormones. The pituitary gland also controls and the menstrual cycle in women.

Thyroid hormones are important because they help kids’ and teens’ bones grow and develop, and they also play a role in the development of the brain and nervous system.

How Does The Thyroid Affect The Body

The thyroid gland is part of the endocrine system. The gland releases hormones into the bloodstream to control your metabolism, which is the primary way your body uses energy. In addition to metabolism, the hormones it releases also help with bone growth, brain development, heart rate, digestion, muscle functioning, body temperature, menstrual cycles, and more. The thyroid can also produce more hormones when needed, such as to help increase body temperature or when a woman is pregnant. If the thyroid gland produces too much or too little hormones some common thyroid disorders can occur, including Hashimotos disease and Graves disease.

Thyroid Gland Largest Endocrine Organ In The Body

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Thyroid gland

Largest Endocrine organ in the body Influence the growth and development of an individual. Involved in production, storage, and release of thyroid hormone Function influenced by Central axis Pituitary function

Secretes hormones; 1) Thyroxine 2) Triiodothyronine . 3) Reverse T 3 4) Calcitonin

Thyroid gland -aggregates of follicles Thyroid follicles spherical in shape Single layer of epithelial cells that surround a central thick solution called colloid Viscous gel like substance contains thyroglobulin

ØAnother type of functional cell ØPARAFOLLICULAR CELLS Øsecrete CALCITONIN that lowers the level of calcium

Chemistry of thyroid gland Derivatives of the amino acid tyrosine bound covalently to iodine. ØThyroxine – 95 -98% ØTriiodotyronine 2 – 5% ØRT 3 Ø T 3 is more active than T 4.

Synthesis of thyroid hormone. Trapping of iodide. Oxidation of iodide to iodine. Thyroglobulin synthesis Iodination of tyrosine. Coupling reaction Proteolysis of thyroglobulin Secretion of thyroid hormones

Trapping of iodide: Secondary Active process by NIS . TSH stimulates this step. Na+ K+ I-

Thiocynate and perchlorate inhibit this iodine trapping

Oxidation of iodide to iodine : Into lumen by transporter pendrin peroxidase. II. TSH promotes this Thiouracil, thiourea, methimazole inhibit this

Coupling reaction: MIT+ DIT = T 3 DIT + MIT= RT 3 DIT + DIT = T 4 Hormones are stored in the cavity of a vesicle rather than the cell itself.

Iodine For Hormone Production

The thyroid gland produces two primary hormones – thyroxine and tri-iodothyronine . The numbers 3 and 4 refer to the number of atoms of iodine in the hormones. Iodine is essential for the production of thyroid hormones and humans need about 150 mcg each day. Iodine is found in most foods, especially seafood. The soils in Tasmania and along the Great Dividing Range are low in iodine, so the food from these areas can contain insufficient iodine. Iodised salt is the best way to supplement dietary iodine, but taking too much iodine can also be a problem.Of the two hormones produced, T3 is more active than T4, but is produced in much smaller quantities. T4 has a lesser effect, but most is converted to T3 by enzymes that remove one iodine atom. The greater the amount of T3 and T4 circulating in the blood, the faster the metabolism. Lower amounts of T3 and T4 result in a reduced metabolism.

What Does The Endocrine System Do And How Does It Work

Thyroid gland: cells, tissues, labeled diagram (preview) – Human Histology | Kenhub

Your endocrine system continuously monitors the amount of hormones in your blood. Hormones deliver their messages by locking into the cells they target so they can relay the message.

The pituitary gland senses when your hormone levels rise, and tells other glands to stop producing and releasing hormones. When hormone levels dip below a certain point, the pituitary gland can instruct other glands to produce and release more. This process, called homeostasis, works similarly to the thermostat in your house. Hormones affect nearly every process in your body, including:

  • Metabolism .
  • Growth and development.
  • Sleep.
  • Blood pressure.

Sometimes glands produce too much or not enough of a hormone. This imbalance can cause health problems, such as weight gain, high blood pressure and changes in sleep, mood and behavior. Many things can affect how your body creates and releases hormones. Illness, stress and certain medications can cause a hormone imbalance.

Endocrine Glands And Organs

The main glands and organs of the endocrine system include:

Other lesser known endocrine organs include:

  • Adipose tissue is recognised to be metabolically important. It releases hormones such as leptin, which affect appetite, and is also a site of oestrogen production. Insulin also acts on adipose tissue.
  • Kidneys produce erythropoietin which stimulates red blood cell production, produce renin which is needed for blood pressure regulation and produce the active form of Vitamin D
  • Gut an increasing number of hormones in the gut are being researched and being understood to effect metabolism and appetite. Included are glucagon-like peptide 1 , ghrelin which stimulates appetite, and somatostatin.

Role Of The Thyroid Gland

The thyroid gland is the primary endocrine gland involved in development and one of the largest endocrine glands in the body. It is positioned on the neck just below the larynx and has two lobes, one on either side of the trachea. It is involved in the production of the hormones T3 and T4 . These hormones increase the metabolic activity of the bodys cells. A deficiency of iodine in the diet leads to the enlargement of the thyroid gland, known as a simple goiter. The thyroid also produces and releases the hormone calcitonin , which contributes to the regulation of blood calcium levels. Thyrocalcitonin decreases the concentration of calcium in the blood. Most of the calcium removed from the blood is stored in the bones.

Thyroid system: The thyroid gland controls how quickly the body uses energy, makes proteins, and how sensitive the body is to other hormones.

The thyroid gland is a two-lobed gland that manifests a remarkably powerful active transport mechanism for the uptake of iodide ions from the blood. As blood flows through the gland, iodide is converted to an active form of iodine, which combines with an amino acid called tyrosine. Two molecules of iodinated tyrosine then combine to form thyroxine. The normal thyroid gland may store several weeks supply of thyroxine in this bound form. 

Functions Of The Endocrine System

The Endocrine system controlsand regulates the complex activities of the body. The Endocrinesystem regulates the activities of the body by secreting complexchemical substances into the blood stream. Thesesecretions come from a variety of glands which control variousorgans of the body. The key functions are:

  • To regulate the metabolic functions of the body.
  • To regulate the rate of chemical reactions in various cells.
  • To influence the ability of substances to transport themselves through cell membranes.

Who Tells The Thyroid To Produce And Release Hormones

Endocrine system hand

The signal comes from a small gland located at the bottom of our brain called the pituitary gland. The pituitary gland produces and sends out a hormone called thyroid-stimulating hormone . TSH then tells the thyroid gland how much hormones to produce and secrete. TSH levels in your blood are rising and falling depending on your bodys needs to produce more or less thyroid hormones.

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 in turn stimulates the release of TSH in the pituitary, which then signals to the thyroid gland.

This whole network is also referred to as the hypothalamic-pituitary-thyroid axis and it adapts to metabolic changes and your bodys needs.

Diseases Of The Endocrine System

Hormone levels that are too high or too low indicate a problem with the endocrine system. Hormone diseases also occur if your body does not respond to hormones in the appropriate ways. Stress, infection and changes in the blood’s fluid and electrolyte balance can also influence hormone levels, according to the National Institutes of Health.

The most common endocrine disease in the United States is diabetes, a condition in which the body does not properly process glucose, a simple sugar. This is due to the lack of insulin or, if the body is producing insulin, because the body is not working effectively, according to Dr. Jennifer Loh, chief of the department of endocrinology for Kaiser Permanente in Hawaii.

Diabetes can be linked to obesity, diet and family history, according to Dr. Alyson Myers of North Shore-LIJ Health System. “To diagnose diabetes, we do an oral glucose tolerance test with fasting.”

It is also important to understand the patient’s health history as well as the family history, Myers noted. Infections and medications such as blood thinners can also cause adrenal deficiencies.

Hormone imbalances can have a significant impact on the reproductive system, particularly in women, Loh explained.  

How Can I Keep My Endocrine System Healthy

Your endocrine system needs the same things the rest of your body needs to stay healthy. You should exercise, eat right and see your healthcare provider regularly.

If you have a family history of diabetes, thyroid disorders or PCOS, talk to your provider. Managing these conditions can help you avoid a hormone imbalance that can lead to health problems.

How Does The Thyroid Gland Work

The thyroid gland is a vital hormone gland: It plays a major role in the metabolism, growth and development of the human body. It helps to regulate many body functions by constantly releasing a steady amount of thyroid hormones into the bloodstream. If the body needs more energy in certain situations for instance, if it is growing or cold, or during pregnancy the thyroid gland produces more hormones.

This organ is found at the front of the neck, under the voice box. It is butterfly-shaped: The two side lobes lie against and around the windpipe , and are connected at the front by a narrow strip of tissue.

The thyroid weighs between 20 and 60 grams on average. It is surrounded by two fibrous capsules. The outer capsule is connected to the voice box muscles and many important vessels and nerves. There is loose connective tissue between the inner and the outer capsule, so the thyroid can move and change its position when we swallow.

The thyroid tissue itself consists of a lot of small individual lobules that are enclosed in thin layers of connective tissue. These lobules contain a great number of small vesicles called follicles which store thyroid hormones in the form of little droplets. 

Thyroid gland cells

The thyroid gland produces three hormones:

  • Triiodothyronine, also known as T3
  • Tetraiodothyronine, also called thyroxine or T4
  • Calcitonin

Growth Hormone / Insulin

video 7 endocrine system thyroid, parathyroid, pineal gland

Somatopause is a term used to describe the change in GH/IGF-I axis, which involves a decrease in production and sensitivity to GH and IGF-I. Typically, GH secretion declines 14% with each decade of life. In the developing human body, GH from the anterior pituitary gland stimulates production and release of IGF-I by the liver, which is then transported in the blood to stimulate growth of muscle and bone.

Decreases in IGF-I signaling, GH deficiency, and GH resistance cause delayed aging and extended lifespan in animal models, in sharp contrast to the effects of GH/IGF-I in humans. Declines in pituitary GH secretion are associated with loss of skeletal muscle mass, increased adiposity, and other detrimental effects of aging in elderly adults. The reason for the opposing actions of GH/IGF-I in different species is not presently understood.

With aging, a decrease in the amount of circulating GH and consequently IGF-I results in weaker bones with a low bone mineral density . In addition to lower circulating amounts of IGF-I, the responsiveness of bone to this protein has been shown to decrease in animal models. This can be attributed to a decrease in IGF-I signaling pathways with advanced cell age. Binding of IGF-I to its receptors normally initiates signaling cascades involving phosphorylation of extracellular signal related kinase and cyclin-dependent kinase . These two pathways combine to promote osteoblast proliferation and survival.

The Role Of Calcium In The Human Body And How The Parathyroid Glands Control All Calcium Levels In Our Bodies

First a word about CALCIUM and what it does in our bodies. We use many elements in our bodies to perform all the different functions of life. Calcium is essential to life, and is used primarily for three things:

  • To provide the electrical energy for our nervous system.  The most important thing that calcium does in the human body is provide the means for electrical impulses to travel along nerves. Calcium is what the nervous system of our body uses to conduct electricity. This is why the most common symptoms of parathyroid disease and high calcium levels are related to the nervous system . Much more about symptoms of parathyroid disease on another page.
  • To provide the electrical energy for our muscular system.  Just like the nerves in our bodies, our muscles use changes in calcium levels inside the cells to provide the energy to contract. When the calcium levels are not correct, people can feel weak and have muscle cramps.
  • Thyroid Hormones: T4 And T3

    There are two main thyroid hormones produced by the follicles: thyroxine , which contains four iodide ions and is represented by the structural diagram below , and triiodothyronine , which contains three iodide ions. T3 is much more powerful than T4, but T4 makes up about 90 per cent of circulating thyroid hormone, and T3 makes up only about ten per cent. However, most of the T4 is converted to T3 by target tissues.

    Figure 9.5.3 This structural model represents a single molecule of thyroxine . The Is represent the four iodide ions it contains. The rings consist mainly of carbon atoms.

    Like steroid hormones, T3 and T4 cross cell membranes everywhere in the body and bind to intracellular receptors to regulate gene expression. Unlike steroid hormones, however, thyroid hormones can cross cell membranes only with the help of special transporter proteins. Once inside the nucleus of cells, T3 and T4 turn on genes that control protein synthesis. Thyroid hormones increase the rate of metabolism in cells, allowing them to absorb more carbohydrates, use more energy, and produce more heat. Thyroid hormones also increase the rate and force of the heartbeat. In addition, they increase the sensitivity of cells to fight-or-flight hormones .

    Figure 9.5.4 The thyroid system is a negative feedback loop that includes the hypothalamus, pituitary gland, and thyroid gland. As this diagram shows, thyroid hormones increase the effect of catecholamines such as adrenaline, a fight-or-flight hormone.

    The Role Of The Parathyroid Glands

    The ONLY purpose of the parathyroid glands is to regulate the calcium level in our bodies within a very narrow range so that the nervous and muscular systems can function properly. This is all they do. They measure the amount of calcium in the blood every minute of every day… and if the calcium levels go down a little bit, the parathyroid glands recognize it and make parathyroid hormone which goes to the bones and takes some calcium out and puts it into the blood. When the calcium in the blood is high enough, then the parathyroids shut down and stop making PTH.

    The single major disease of parathyroid glands is over-activity of one or more of the parathyroids which make too much parathyroid hormone causing a potentially serious calcium imbalance . This is called hyperparathyroidism and this is the disease that this entire web site is about.

    Other Thyroid Gland Disorders

    The Thyroid: Your Bodyâs Powerhouse Gland

    Other disorders of the thyroid gland include:

    • Nodules – lumps in the thyroid. Some are groups of uncontrollably overactive thyroid cells. These are called hot nodules and cause hyperthyroidism. Other nodules are cold. These are generally harmless, but about 20 per cent will be cancerous.
    • Cancer – thyroid cancer is uncommon and is readily treatable, especially if detected early.

    How Can I Promote The Health Of The Thyroid Gland

    Iodine is most essential to maintain a healthy thyroid. Iodine is the critical ingredient for the production of thyroid hormones. We dont need a lot of iodine, it is said that one teaspoon of iodine is enough for a lifetime. Nonetheless, the daily and constant supply of this micronutrient is important. Too much iodine at once is counter-productive and causes your thyroid to produce less hormones. The best way to get your daily dose of iodine is through eating healthy foods like seafood and dairy products. In addition, iodized salt is a good source and you can use it to season your food. Nowadays, iodine is added to salt to combat goitres .

    The Role Of The Thyroid Gland

    The thyroid is a gland in the neck, just below the voicebox. It is an endocrine gland. Endocrine glands make hormones. These are chemicals that carry messages through the bloodstream to other parts of the body. The thyroid gland makes thyroid hormones. The thyroid gland is managed by the pituitary gland, which sits at the base of the brain.

    What Is The Endocrine System

    Your endocrine system is made up of several organs called glands. These glands, located all over your body, create and secrete hormones.

    Hormones are chemicals that coordinate different functions in your body by carrying messages through your blood to your organs, skin, muscles and other tissues. These signals tell your body what to do and when to do it.

    Milestones In The Study Of The Endocrine System

    The Thyroid Gland | Complete Anatomy

    200 B.C.: The Chinese begin isolating sex and pituitary hormones from human urine and using them for medicinal purposes

    1025: In medieval Persia, the writer Avicenna provides a detailed account on diabetes mellitus in “The Canon of Medicine” , describing the abnormal appetite, the collapse of sexual functions and the sweet taste of diabetic urine.

    1835: Irish doctor Robert James Graves describes a case of goiter with bulging eyes . The thyroid condition Graves’ disease was later named after the doctor.

    1902: William Bayliss and Ernest Starling perform an experiment in which they observe that acid instilled into the duodenum causes the pancreas to begin secretion, even after they had removed all nervous connections between the two organs.

    1889: Joseph von Mering and Oskar Minkowski observe that surgically removing the pancreas results in an increase of blood sugar, followed by a coma and eventual death.

    1921: Otto Loewi in 1921 discovers neurohormones by incubating a frog’s heart in a saline bath.

    1922: Leonard Thompson, at age 14, is the first person with diabetes to receive insulin. Drugmaker Eli Lilly soon starts mass production of insulin.

    Additional reporting by Alina Bradford, Live Science contributor.

    Editors Note: If youd like more information on this topic, we recommend the following book:

    What Could Go Wrong With The Thyroid Gland

    Normally the thyroid gland produces the exact number of hormones needed to keep your bodys metabolism running and in balance. As described earlier, hormones secreted by the pituitary gland 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 or your thyroid doesn’t produce enough hormone , resulting in your body using energy faster or slower than it should.


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