Thyroid Gland and its Functions

Thyroid Gland and its Secretions

Thyroid is an endocrine gland situated in the front of neck. It consists of two lobes, lying one on each side of the trachea just below the larynx. Both the lobes are joined by narrow band of thyroid tissue called isthmus of thyroid. The gland receives very rich supply of blood and consists of a large number of vesicles formed by secreting cells grouped around the small cavities called alveoli. The thyroid alveoli contain very thick colloid or gummy substance, composed of thyroxine hormone, which is rich in iodine content. Secreting cells of the vesicles contain an internal secretion known as thyroglobulin which is broken down to thyroxine and released in the alveoli of thyroid. The thyroid gland governs the general metabolism of all body tissues. The triiodothyronine (T3) hormone is also present in the colloid of thyroid gland and blood plasma. The triiodothyronine (T3) has been found to be more active than thyroxine. Thyroxine is an iodine derivative of thyronine. Thyroxine has four iodine atoms in its molecule and could also be called T4 hormone. The function of thyroid is regulated by thyrotrophic hormone of the anterior lobe of pituitary gland. Normally thyroid is not palpable but may get enlarged where there is deficiency of iodine in water supply. Enlarged thyroid could be associated with non-toxic or toxic goitre. Goitrous gland may have normal function or under function (hypothyroidism) or over function (hyperthyroidism). Suboptimal activity of thyroid gland at birth leads to hypo-secretion of thyroid hormones and causes cretinism. Cretinism is a disorder of thyroid in which mental and physical growth are retarded.

Functions of Thyroid Gland

The thyroid gland controls the body metabolism in terms of temperature, pulse rate, respiratory rate, cardiac output, appetite, body weight, emotions, nervous temperament and intelligence. Though it looks strange to put the emotions, nervous temperament and intelligence under the metabolic functions but it is true that the metabolic changes influence all these. Thyroid gland and its iodine containing hormones play a vital role in metabolic processes of our body essential for good health.