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Thyroid gland is a gland (two lobes) located underneath the larynx or the voice box. These lobes produce a hormone called thyroxine in our bodies. It also produces calcitonin, a hormone that helps to control the calcium and phosphate level in the blood. This endocrine gland helps in regulating the metabolism and the overall development of the human body.
What is a Thyroid Gland?
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Thyroid gland is a gland (two lobes) located underneath the larynx or the voice box. These lobes produce a hormone called thyroid in our body. It also produces calcitonin, a hormone that helps to control the calcium and phosphate level in the blood. This endocrine gland helps in regulating the metabolism and the overall development of the human body.
The Thyroid gland administers the regulation of the release of thyroid hormones in the bloodstream. Thus, the Thyroid gland will manage to release additional hormones, in case a body needs more energy.
Anatomy of Thyroid Gland
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The medical term of the Thyroid gland is Glandula Thyreoidea. The Thyroid gland is positioned on both sides of the trachea under the larynx and the lobes are attached at the anterior (front) of the neck by a band of tissue. This gland ordinarily weighs around 20 grams to 60 grams. This gland has a rich number of blood vessels connected to it.
Hormones of Thyroid Gland
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The tissue of the Thyroid gland contains a plethora of tiny lobules embedded in the layers of connective tissues which further contain sacs called follicles. These follicles contain Thyroid Hormones. The major hormones that the Thyroid gland produces are:
- Tetraiodothyronine (Thyroxine) or T4 hormone
- Triiodothyronine or T3 hormone
- Calcitonin
The Thyroxine hormone and the Triiodothyronine hormone (the T3 and the T4 hormone) takes iodine as the major constituents. Since iodine cannot be produced in the human body, it needs to be taken ingested especially through our diet. The hormones that the Thyroid gland produces play a major role in brain development in children.
One more hormone that is produced by the Thyroid gland is known as Calcitonin. This hormone is produced by the C-cells. It mainly regulates the metabolism of our bones and the calcium in our bodies.
Disorders in Thyroid Gland
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When there is an imbalance in bodily functions, the thyroid gland can get affected which directly impacts the secretion of the hormones in our bodies. These disorders either lead to the over-secretion of the hormones or under-secretion of thyroid hormones in the human body. The Thyroid gland is usually affected by two kinds of conditions such as:
- Hyperthyroidism
- Hypothyroidism
Hyperthyroidism: It is the excess secretion of the hormones by the thyroid gland into the bloodstream.
Hypothyroidism: It is the state where when the required hormones are not secreted in sufficient quantities by the Thyroid gland in our bodies.
The key differences between these conditions are tabulated below:
| Hyperthyroidism | Hypothyroidism |
|---|---|
| Occurs due to excessive production of thyroid hormones | Occurs due to insufficient production of thyroid hormones |
| Symptoms of slow metabolism occur | Symptoms of relatively higher metabolism occur |
| Hashimoto’s disease is a common cause | Grave’s disease is a common cause |
| It is characterized by an increase in weight despite poor appetite. | It results in loss of weight even with increased appetite. |
| Intolerable to cold | Intolerable to heat |
| TSH levels will increase | TSH levels will decrease or be normal. |
| It is usually treated with a man-made thyroid supplement hormone called L-Thyroxine. | It is usually treated with pharmaceutical methods, radiotherapy and surgical removal. |
These abnormal conditions of the Thyroid gland can lead to a number of disorders such as:
Goitre
It is the enlargement or the swelling of the Thyroid gland. The abnormal enlargement of the Thyroid gland itself is known as the Diffuse Goitre and the abnormal growth in the nodules in the gland is known as Nodular Goitre. Goitre is caused due to the deficiency of iodine in the human body.
Thyroiditis
The other abnormalities of the Thyroid gland include Thyroiditis which is an inflammation of the Thyroid gland caused particularly because of the viral infection in the throat.
Grave’s Disease
Hyperthyroidism may sometimes lead to Graves’ disease which is an autoimmune condition where the affected person experiences symptoms like bloated or swollen eyes, loss of weight, osteoporosis, heart problems etc.
Thyroid Cancer
The deviations in the normal mechanism of the Thyroid gland can even cause Thyroid cancer. It is a cancer that affects the Thyroid gland and is mostly curable. Thyroid cancer is an uncommon type of cancer that may need surgery or hormone therapies to cure.
Thyroid Disorders Treatment
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Severe cases of thyroid disorders may require radioactive iodine therapy or Levothyroxine hormone replacement therapy. Other moderate cases can be cured by the use of medication and a well-balanced diet.
Things to Remember
- The Thyroid gland is a gland (two lobes) located underneath the larynx or the voice box.
- The Thyroid gland produces thyroid hormones.
- The Thyroid hormones include Triiodothyronine (T3), Tetraiodothyronine (T4), and Calcitonin hormones. The two major thyroid hormones are T3 and T4 hormones.
- Calcitonin is produced in the C-cells.
- The Thyroid gland ordinarily weighs around 20 grams to 60 grams.
- The Thyroid gland usually has two abnormalities in its performance: Hyperthyroidism and Hypothyroidism
- The irregularities in the production and release of the Thyroid hormones may lead to various diseases like Goiter, Thyroiditis, Thyroid Cancer, and Graves’ disease.
- The Thyroid gland knows when to release how much of the hormones. For example, when the body is in need of more energy, the gland produces and releases more hormones.
- The Thyroid gland uses iodine as a constituent for the production of thyroid hormones.
Sample Questions
Ques. What is Radioactive iodine therapy? (2 marks)
Ans. In some cases, radioactive iodine is used to treat an overactive thyroid gland. The radioactive iodine is taken orally and reaches the thyroid gland through the bloodstream, destroying thyroid cells. The treatment results in a diminished size of the goitre. Excessive intake might eventually lead to an underactive thyroid gland.
Ques. What are the effects of Hypothyroidism during pregnancy? (2 marks)
Ans. Hypothyroidism during pregnancy causes defective development and maturation of the growing baby leading to stunted growth (cretinism), mental retardation, low intelligence quotient, abnormal skin, deaf-mutism etc.
Ques. Describe the anatomy of the Thyroid gland. (2 marks)
Ans. Thyroid gland is a gland (two lobes) located underneath the larynx or the voice box. These lobes produce a hormone called thyroid in our body. It also produces calcitonin, a hormone that helps to control the calcium and phosphate level in the blood. This endocrine gland helps in regulating the metabolism and the overall development of the human body.
Ques. What are the treatment methods of Goitre? (2 marks)
Ans. For hypothyroidism, thyroid hormone replacement with levothyroxine (Levoxyl, Synthroid, Tirosint) will resolve the symptoms of hypothyroidism as well as slow the release of thyroid-stimulating hormone from your pituitary gland, often decreasing the size of the goitre.
Ques. What are the hormones produced by the Thyroid gland? (2 marks)
Ans. The tissue of the Thyroid gland contains a plethora of tiny lobules embedded in the layers of connective tissues which further contain sacs called follicles. These follicles contain Thyroid Hormones. The major hormones that the Thyroid gland produces are:
- Tetraiodothyronine (Thyroxine) or T4 hormone
- Triiodothyronine or T3 hormone
- Calcitonin
Ques. Calcium plays a very important role in the formation of bones. Write on the role of endocrine glands and hormones responsible for maintaining calcium homeostasis. (2 marks)
Ans. Thyroid gland and parathyroid gland are responsible for maintaining calcium homeostasis. Both act antagonistic to each other. Thyroid gland secretes the hormone calcitonin when calcium level is high in the blood. It then lowers the calcium level by suppressing the release of calcium ions from the bones. Parathyroid glands secrete the hormone parathormone. It increases the Ca2+ level in the blood. It acts on bones and stimulates the process of bone resorption. Parathormone also stimulates reabsorption of Ca2+ by the renal tubules and increases Ca2+ absorption from the digested food. Thus parathormone, along with calcitonin plays a very important role in calcium balance in the body.
Ques. What are the uses of T3 and T4 hormones? (2 marks)
Ans. The Thyroxine hormone and the Triiodothyronine hormone (the T3 and the T4 hormone) takes iodine as the major constituents. Since iodine cannot be produced in the human body, it needs to be taken ingested especially through our diet. The hormones that the Thyroid gland produces play a major role in brain development in children.
Ques. What is Calcitonin? (2 marks)
Ans. One more hormone that is produced by the Thyroid gland is known as Calcitonin. This hormone is produced by the C-cells. It mainly regulates the metabolism of our bones and the calcium in our bodies.
Ques. What are the abnormal conditions that arise in the thyroid gland? (2 marks)
Ans. When there is an imbalance in bodily functions, the thyroid gland can get affected which directly impacts the secretion of the hormones in our bodies. These disorders either lead to the over-secretion of the hormones or under-secretion of thyroid hormones in the human body. The Thyroid gland is usually affected by two kinds of conditions such as:
- Hyperthyroidism
- Hypothyroidism
Ques. Differentiate Hyperthyroidism and Hypothyroidism. (2 marks)
Ans.
| Hyperthyroidism | Hypothyroidism |
|---|---|
| Occurs due to excessive production of thyroid hormones | Occurs due to insufficient production of thyroid hormones |
| Symptoms of slow metabolism occur | Symptoms of relatively higher metabolism occur |
| Hashimoto’s disease is a common cause | Grave’s disease is a common cause |
| It is characterized by an increase in weight despite poor appetite. | It results in loss of weight even with increased appetite. |
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