250px-Illu thyroid parathyroid

Thyroid with parathyroid glands


In vertebrate anatomy, the thyroid gland or simply, the thyroid, is one of the largest endocrine glands in the body, and is not to be confused with the "parathyroid glands" (a completely different set of glands). The thyroid gland is found in the neck, inferior to (below) the thyroid cartilage (also known as the 'Adam's Apple') and at approximately the same level as the cricoid cartilage. The thyroid controls how quickly the body uses energy, makes proteins, and controls how sensitive the body should be to other hormones.

The thyroid gland participates in these processes by producing thyroid hormones, the principal ones being triiodothyronine (T3) and thyroxine (T4). These hormones regulate the rate of metabolism and affect the growth and rate of function of many other systems in the body. T3 and T4 are synthesized utilizing both iodine and tyrosine. The thyroid gland also produces a hormone called 'calcitonin', which plays a role in calcium homeostasis.

The thyroid gland is controlled by the hypothalamus and pituitary (to be specific, the anterior pituitary). The thyroid gland gets its name from the Greek word for "shield", after the shape of the related thyroid cartilage. The most common problems of the thyroid gland consist of an over-active thyroid gland, referred to as 'hyperthyroidism', and an under-active thyroid gland, referred to as 'hypothyroidism'.


Disorders of the thyroid gland fall into the following categories:


Hyperthyroidism is an overactive thyroid. It is the overproduction of the "thyroid hormones" (T3 and T4) by the thyroid gland to which hyperthyroidism refers. The most common cause of hyperthyroidism is a disease called "Graves' Disease". Graves' Disease is a 'diffuse toxic goiter' in which the thyroid gland enlarges as a result of the thyroid glands' overproduction of the T3 & T4 hormones.

Graves' disease is considered to be an autoimmune disease and is the most common cause of thyroid gland over-activity (hyperthyroidism). Graves' disease is much more common in women than in men. Graves' Disease results from excess stimulation of the thyroid gland and usually presents with symptoms in the 2-3rd decade of life. Symptoms include: An enlarged thyroid (goiter), protruding eyes (exopthalmos), palpitations, excess sweating, diarrhea, weight loss, muscle weakness and unusual sensitivity to heat. One treatment of Grave's disease involves the patient taking an oral dose of radioactive iodine, resulting in permanent destruction of cells in the thyroid, thus rendering them permanently inactive. The patient may then be treated with daily replacement hormone therapy as a result of a new found hypothyroidism. Another option may be surgery in which the thyroid gland is partially/fully removed.


Hypothyroidism is the underproduction of "thyroid hormones" (T3 and T4). Hypothyroid disorders occur when the thyroid gland is inactive or under-active as a result of improper formation from birth, or the removal in whole or the removal in part of the thyroid gland.

Symptoms include: abnormal weight gain, tiredness, baldness, temperature intolerance (both heat and cold), and palpitation.


Beta blockers are used to decrease symptoms like tachycardia, tremors, anxiety and chest palpitations, and are sometimes anti thyroid drugs used to block thyroid hormones, in particular, in the case of Graves' disease. These medications take several months to take full effect and have side-effects like skin rash or a drop in white blood cell count, which decreases the ability of the body to fight off infections. Sometimes these drugs involve frequent dosing (such as one synthroid pill each 24 hours) and require frequent doctor visits (blood tests) to track impacts and progress, and sometimes may be ineffective at free. Because of the side-effects and treatment protocol of drugs, many patients choose to undergo surgery or more commonly the use of radioactive iodine 131, a type of radioiodine treatment. Sometimes, radioiodine is administered under a thyroid ablation procedure to severely restrict or altogether destroy the gland; the radioactive iodine is selectively taken up by the gland and gradually thins out producing cells and destroys the tissues. The treatment has been noted to be safe and effective.

Individuals that have under-activity of the thyroid gland require hormone replacement therapy. Several types of thyroid hormone replacements are available and all are very safe but need to be taken for the rest of one's life. Thyroid hormone treatment is given under the care of a physician and may take a few weeks to become effective.[1]

Surgery is sometimes used to treat overactive thyroid, thyroid nodules, and often for thyroid cancers. The surgery is quite effective but can have a few side-effects or risks:

  • The nerves controlling the vocal cords can be damaged.
  • The parathyroid glands that produce parathyroid hormone (PTH) can be destroyed and one can develop bleeding.
  • If the entire thyroid gland is removed, one develops hypothyroidism, which entails taking hormone supplements for the rest of one's life.[2]


  1. Thyroid Disorders Information MedicineNet. Retrieved on 2010-02-07
  2. Thyroid Problems eMedicine Health. Retrieved on 2010-02-07


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