Hormones secreted by thyroid gland, Biology

Hormones. The thyroid gland secretes following hormones.

Thyroxine (tetraiodothyronine or T4)' and tri-iodothyronine or T3 are secreted by the thyroid follicular cells.

Calcitonin is secreted by the C-cells of the thyroid gland.

(i) Thyroxine (T4) and Tri-iodothyronine (T3) T4 and T3 contain four and three atoms of iodine.

T3 is secreted in smaller amounts (10%) but it is more active and several times more potent than T4

T is converted into Tby removal of one iodine in the liver, kidneys and some other tissues.

T4 and T3 have similar effects on the target cells, they are generally considered together under the name, thyroid hormone (TH).

The thyroid gland is the only gland that stores its hormones in large quantity.

T4 and T3 are synthesised by attaching iodine to the aminoacid tyrosine.

Function of T3 & T4  -

(a) They regulate the metabolic rate of the body and thus maintain basal metabolic rate (BMR)

(b) They stimulate protein synthesis and, therefore, promote growth of the body tissues.

(c) They regulate the development of mental faculties.

(d) As they increase heat production, thus they maintain body temperature.

(e) They help in metamorphosis of tadpole into adult frog. If thyroid gland of the tadpole (larva) is removed, the larva fails to change into an adult.

(f) They increase action of neurotransmitters like adrenaline and noradrenaline.

(ii) Calcitonin (CT). It is secreted when calcium level is high in the blood. It then lowers the calcium level by suppressing release of calcium ions from the bones. Thus calcitonin has an action opposite to that of the parathy- roid hormone on calcium metabolism.

Posted Date: 10/2/2012 6:46:35 AM | Location : United States







Related Discussions:- Hormones secreted by thyroid gland, Assignment Help, Ask Question on Hormones secreted by thyroid gland, Get Answer, Expert's Help, Hormones secreted by thyroid gland Discussions

Write discussion on Hormones secreted by thyroid gland
Your posts are moderated
Related Questions
Q. Explain about Congestive Cardiac Failure? It is an end stage heart disease and a significant contributor to morbidity and mortality particularly in the elderly population. C

Explain the Air Sampling? Microorganisms may be present in air of processing facility and have an impact on the quality and safety of foods processed and handled there. To avoi

Explain the Lamarck's Theory in evolution? Prior to Darwin, most people believed in and held to the creationist viewpoint that species were created in their current forms, whic

Q. What is the function of the plant cell wall? The plant cell wall has protective and structural functions. It plays an significant role in the constraint of the cell size, pr

Q. Which are nucleotides "portions" that to bind in the formation of nucleic acids? What is meant by the 5' and 3' extremities of the nucleic acids? The phosphate group of one

(a) What are the two main pollutants that contribute to acid rain? (b) Where do these pollutants come from? (c) What direct or indirect effect is 'acid rain

Explain Adverse effects of Zidovudine  It include anemia, neutropenia, nausea, vomiting, headache, fatigue, confusion, malaise, myopathy, hepatitis, and hyperpigmentation of or

A large number of plants are used for bio-pesticides and bio-fertilizers. Several plant species are used as insecticides against aphids and larvae of insect pests: for insects like

Diseases Caused by Viruses In the early days of microbiology, the disease producing submicroscopic agents were termed as 'filterable viruses' because of their ability to pass t

Alternative Therapies Assignment 1. A. Acupunture, B.  Osteopathy, C.  Herbal therapy For each one of alternative therapies above, answers the three questions below! 1. Th