THYROID GLAND

                 THYROID GLAND

Thyroid gland: A gland that makes and stores hormones that help regulate the heart rate, blood pressure, body temperature, and the rate at which food is converted into energy. Thyroid hormones are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism) in the body. Thyroid hormones also help children grow and develop.

In vertebrate anatomy, the thyroid gland or simply, the thyroid, is one of the largest endocrine glands in the body . 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, principally 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 (specifically, 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

Disorders of the thyroid gland fall into the following categories:

Hyperthyroidism

Hyperthyroidism in 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.

Symptoms include: An enlarged thyroid (goitre), protruding eyes (exopthalmos), palpitations, excess sweating, diarrhea, weight loss, muscle weakness and unusual sensitivity to heat. 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.

Hypothyroidism

Hypothyroidism is the underproduction of "thyroid hormones" (T3 and T4). Hypothyroid disorders occur when the thyroid gland is inactive or underactive 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.

 Enlargement of the thyroid

An enlarged thyroid gland can exist and not be considered "hyperthyroidism". The term "Non-toxic goiter" (or simply 'Goiter') is used when enlargement of the thyroid gland occurs-but only if the enlargement is not as a result of hyperthyroidism (not due to the overproduction of a thyroid hormone), nor due to a malignancy. Only then can the condition be deemed a "Non-toxic Goiter" (or simply 'Goiter') for short. This enlargement, the 'goiter', can occur when iodine is not in the diet in sufficient amounts. Goiter due to iodine deficiency is uncommon in developed countries as various food items come standard with added iodine (i.e.: Seasoning-type table salt is supplemented with iodine). Iodine deficiency is still observed in some developing parts of the world.

Additionally, enlargement of the thyroid can also occur as a result of a bacterial infection or a viral infection. When this occurs it is deemed 'Thyroiditis'.

Goiter typically takes many years to present.

Cancers

Cancers do occur in the thyroid gland and, in general, are more common in females. In most cases, the thyroid cancer presents as a painless mass in the neck. It is very unusual for the thyroid cancers to present with symptoms, unless it has been neglected. One may be able to feel a hard nodule in the neck. Diagnosis is made using a needle biopsy and various radiological studies. All thyroid cancers are treated with surgery.

Non-cancerous nodules

Many individuals may find the presence of small masses (nodules) in the neck. The majority of these thyroid nodules are benign (non cancerous). The presence of a thyroid nodule does not mean one has thyroid disease. Most thyroid nodules do not cause any symptoms, and most are discovered on an incidental exam. Doctors usually perform a needle aspiration biopsy of the thyroid to determine the status of the nodules. If the nodule is found to be non-cancerous, no other treatment is required. If the nodule is suspicious then surgery is recommended..

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