Details & Function of the Thyroid Gland

The thyroid is a large hormone secreting gland located in the neck. It is located below the thyroid cartilage, otherwise known as the Adam's apple, and above the collar bone. The thyroid gland gets its name from the Greek word for "shield" because of the shape of the thyroid cartilage, when in actual fact the thyroid gland itself is shaped more like a butterfly.

Anatomy

• The thyroid gland is composed of two lobes connected by a piece of tissue called an isthmus. It extends down from the thyroid cartilage to the forth or fifth tracheal ring--the semi-circular pieces of cartilage surrounding the trachea. The connecting isthmus between the thyroid lobes lies anterior (toward the front of the body) to the second, third and fourth tracheal rings.

Function

• The thyroid gland controls the body's sensitivity to hormones as well as how quickly the body uses energy and makes proteins. By producing thyroxine, triiodothyronine and calcitonin hormones, the thyroid is able to regulate metabolism and affect the rate of other bodily functions. The hypothalamus and pituitary gland within the brain control the thyroid.

Thyroid Hormone Action

• Thyroxine (T4) and triiodothyronine (T3) hormones are important for brain development in the body during the fetal stage. During childhood, the hormones play a role in the growth and development of the body as well as dictating the speed of the body's metabolism--the chemical processes that synthesize proteins, carbohydrates and fats and break down complex substances in digestion to produce energy and waste matter.

Disorders: Hypothyroidism

• Hypothyroidism or under-active thyroid occurs when the thyroid gland does not produce enough of the thyroxine or triiodothyronine hormones. The condition can be caused by treatment for an over-active thyroid, Hashimoto's thyroiditis--a gradual swelling of the thyroid gland or disease of the pituitary gland or the hypothalamus. Hypothyroidism can be treated with daily hormone replacement pills.

Disorders: Graves' Hyperthyroidism

• Not to be confused with hypothyroidism, Graves' Hyperthyroidism, also known as Graves' Disease and Thyrotoxicosis, is an autoimmune disorder resulting in the excessive production of hormones by the thyroid. It is caused by an abnormal protein within the body called the "thyroid stimulating antibody." As the name suggests, it stimulates the thyroid to produce greater amounts of hormone in an uncontrolled manner. Graves' Hyperthyroidism is a genetically determined abnormality of the immune system and there is no treatment for the underlying cause--symptoms can be controlled by removal of part of the thyroid (thyroidectomy) as well as treatment with radioactive iodine or hormone blocking drugs.