Thyroid Gland Function: Functions and Anatomy of Thyroid Gland

Our endocrine system is made up of several glands and thyroid gland is one of them. The glands produce hormones which are essential for various metabolic process of the body.

Thyroid Gland Anatomy and Location

  • The thyroid is situated below the Adams apple.
  • The normal adult thyroid weighs 15 to 20gm. Its size is equal to the distal phalanx of the thumb of the person.
    It is located in front of the neck. There are two lobes each lies on either side of the wind pipe, joined by a small thyroid tissue called the isthmus. It forms a H shape.
  • In its developmental stage in the womb, thyroid lies behind the tongue, and it migrates in front of the neck at the time of birth. It rarely fails to migrate and stays at the back of the tongue.
  • The blood supply to thyroid is superior and inferior thyroid arteries. Through a rich capillary network, it delivers 0.5 ml blood per g per min.

Thyroid Gland Function

  • The main function of the thyroid is to absorb iodine and convert it into hormones T3 and T4.
    T3 is called triiodothyronine and T4 is called as thyroxin.
  • The absorbed iodine is then combined with amino acid tyrosine to produce T3 and T4 hormones. The hormone thus produced start circulating in the blood and converts consumed calories to produce energy for the cells.
  • The hormones T3 and T4 are produced in the ratio of 20%: 80%. However the strength of T3 is more compared to T4.
  • The regulation of thyroid function involves hypothalamic- pituitary- thyroid axis.
  • Which means the thyroid gland is under the control of pituitary gland located in the brain. When the pituitary gland senses that thyroid hormone level has decreased in the blood, it releases thyroid stimulating hormone. The function of TSH is to stimulate the thyroid cells to produce more of T3 and T4 hormones. As soon as pituitary gland senses that the level of T3 and T4 has increased, it reduces the supply of TSH.
  • The hypothalamus situated in the brain controls the pituitary gland, and it indicates the pituitary to release TSH to stimulate the thyroid. Thus the hypothalamic –pituitary –thyroid axis is completed.
  • The abnormalities of thyroid function can cause various health issues such as Goiter, hypothyroidism, hyperthyroidism, thyroid carcinoma, thyroiditis and thyroid nodule. Etc.

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