Thyroid is an endocrine gland that is small and butterfly shaped. Its weight is less than one ounce and is situated in the front of the neck. It constitutes two lobes that are attached together by a narrow strip of thyroid tissue called isthmus and these lobes lie just along the trachea. Thyroid gland is located below your larynx or Adam’s apple.
Thyroid gland originates from the backside of tongue, when inside the womb, and normally migrates to front of the neck before the birth but in rare case it does not migrate properly and remain in the backside of the tongue or high in the neck. In some cases it migrates away far too much from normal position and extends up to chest.
The thyroid gland is surrounded by two fibrous capsules. Outer capsule is attached to voice box muscles and other important nerves and muscles. Between the outer and inner capsule loose connective tissues are present for the movement of thyroid to alter its position when we swallow. Thyroid gland produces thyroid hormones that travel from thyroid gland to all parts of the body in the bloodstream.
How thyroid works
Thyroid gland acquires iodine from bloodstream and utilizes it to produce thyroid hormones that are T3 or Triiodothyronine, T4 or Thyroxin also called Tetraiodothyronine and Calcitonin. T3 and T4 are main thyroid hormones. These are produced in follicular epithelial cells of thyroid gland. T3 contain 3 atoms of iodine and T4 contain 4 atoms. T3 is formed from T4 when one iodine atom is removed. T3 is mostly used in liver, kidney and brain so conversion of T4 to T3 occurs outside the thyroid in these organs. T4 is stored in microscopic follicles of thyroid and T3 is stored in thyroid. These are produced in bloodstream in desired amount to meet metabolic needs of the cells of the body. Thyroid hormone smoothly slips in the cells that need it and connect to the special receptors of cell’s nuclei.
Role of Pituitary gland
Thyroid gland is controlled by pituitary gland present in the brain. Pituitary gland releases TSH i.e. Thyroid Stimulating Hormone. Thyroid gland produces thyroid hormones when thyroid stimulating hormone is released into the blood stream by pituitary gland. If pituitary gland detects the low levels of thyroid hormone it produces more TSH and if it detects high levels of thyroid hormones, it produces less TSH. Pituitary gland is regulated by hypothalamus gland that is a part of brain. It produces TRH i.e. TSH releasing hormone. Thyroid hormone influences all organs and cells of the body. The only cells that can absorb iodine in the body are thyroid cells. These cells combine acid tyrosine with iodine to form T3 and T4. T3, T4 controls body metabolism i.e. convert calories and oxygen into energy. Metabolism regulation of every cell of the body depends upon thyroid hormone.
Thyroid hormones help in the working of all organs. These affect the metabolism rate of the body that helps to break down the nutrients from food. High levels of thyroid cause hyperthyroidism and low levels cause hypothyroidism. Too fast or too slow working of bodily functions can bring discomfort. Lesser production of thyroid hormone can make you feel cold and tired. On the other hand, excessive production of thyroid hormone can make you feel warm, jumpy and nervous. Thyroid disorders occur mostly in women and rarely in men, children, teenagers and babies.