Structure and functions of the Thyroid Gland

The thyroid gland also called as the master gland really plays a very important role in the human body. Here in this article, let us see about the structure and the functions of the thyroid gland!

Thyroid Gland:

The thyroid gland is one of the endocrine glands of human beings. In human, the thyroid gland is located in the neck region. It is divided into two lobes or chambers. These two lobes are found on the either side of the larynx of the neck and are connected by a narrow bridge of glandular tissue called isthmus which is found in the anterior region of the neck. The two lobes are in turn divided into a number of small chambers called lobules. These lobules have inside them structures called follicles. The follicles are lined by a layer of glandular cubical epithelial cells. The follicles are also called acini (singular – acinus). The cavity inside each acinus is filled by a gelatinous substance called the colloid which contains the hormone called thyroxine. The thyroxine hormone is rich in iodine and hence it is an iodinated hormone. Its major constituent is iodine which contributes for about 65%. The amino acid residue inside the thyroxine hormone is the thyrosine.

Main Functions of the Thyroid Gland:

The thyroid gland is responsible for the normal growth and metabolism of the skeletal and the nervous systems of the body. It controls the cellular oxidation of various tissues of the body. Another important function of the thyroid gland is the maintenance of the Basal Metabolic Rate (BMR). The Basal Metabolic Rate is defined as the amount of heat produced in the human body at a state of complete physical and mental rest at 20o C room temperature.

Other Major Actions of the Thyroid Gland:

The following are the other major functions of the thyroid gland and its secretion that promotes human lives.

  1. The most important function of the thyroid gland is the re-absorption of glucose from the small intestine thus preventing the loss of glucose from the human body.
  2. The thyroid gland plays an important role in the development of the nervous system in children especially at the time of birth.
  3. It promotes the anabolism of protein in human beings thus ensuring growth in children.
  4. Presence of optimum level of thyroxine in the blood maintains efficient functioning of the muscular movements and also plays an important role in the gonadal functions.
  5. The thyroid gland helps in increasing the heart beat rate and force of contraction and it also increases the pulse rate.
  6. It promotes the normal metabolism of tissues except the tissues of brain, accessory sex organs, gonads, lungs, spleen and the lymph nodes.
  7. This hormone reduces the cholesterol level in the serum thus reducing the chances of getting affected by heart diseases.

However, deficient or over secretion of the thyroxine can lead to several diseases and let us see them below.


Hyperthyroidism is nothing but the physiological effect caused in the human body by over secretion of the thyroid hormone (thyroxine). The other names of hyperthyroidism are Grave's disease, thyrotoxicosis and exophthalmic goiter. The main effects caused by hyperthyroidism are high Basal Metabolic Rate (BMR), increased pulmonary ventilation, increased rate of heart beat, nervousness, emotional instability, protrusion of eyeballs from the socket (exopthalmus)loss of weight, less amount of serum cholesterol, high glucose level in the blood and derangement of sexual functions. However, hyperthyroidism can be cured by treatment and by reducing the amount of intake of salt (iodine).


Hypothyroidism is the opposite to hyperthyroidism, i.e. the physiological effects that is caused due to deficiency in the production of thyroid glands. This is due to inadequate amount of iodine intake in the diet. Due to less iodine intake, there is a fall in the production level of thyroxine and hence increased production of the Thyroid Stimulating Hormone (TSH) occurs due to which hypertrophy of the thyroid gland takes place. It is recommended to take in at least 500 micro grams of iodine daily. Hypothyroidism can cause three types of diseases in human beings as follows.

Simple Goiter:

Simple goiter other wise known as endemic goiter is common among the people those who live in hilly areas where there is less amount of iodine present in the soil. This disease is characterized by enlarged thyroid gland and hence those persons have a big throat region. This disease can be treated by intake of sufficient amount of iodine regularly. This disease is not a spreading or a regional disease but it occurs in all the regions of the world where there is less amount of iodine in the soil.


This disease occurs in children who have deficiency in the secretion of the thyroid gland right from the period of birth. The consequences of cretinism are protruding tongue and abdomen, high BMR, subnormal body temperature, short stature, retarded skeletal growth, mental retardation to extreme degrees and arrest of pubertal sexual maturity.


This disease is cause usually in adults due to deficiency in the secretion of the thyroxine gland. The person who is affected by this disease has the following characteristics:

  • low Basal Metabolic Rate
  • dry, coarse and sparse hair
  • scaly and dry skin
  • low Blood Pressure (B.P)
  • anemia with increased cholesterol in the serum
  • hoarse voice and a slow speech
  • slow thinking process and poor memory
  • weakness of the muscles and muscle fatigue, etc.


Hence, there is no doubt that the thyroid gland is the most important of all the endocrine glands and hence it should be cared well. Hence, whenever you buy a salt from the shop, first make sure that the salt is an ionized salt that is approved by the government and thus the serious consequences of the imbalance amount of the thyroxine hormone can be prevented.

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