Welcome to the Endocrine discussion. For this discussion you will need to post a

Question

Welcome to the Endocrine discussion.

For this discussion you will need to post an in-depth answer written in your own words to the following question:

Discuss the function of the thyroid gland.

Grading Rubric:

Post must be at least 200 words.

Post completely written in your own words.

Includes a brief discussion about the cells of the thyroid gland.

Includes a description of the hormones secreted by the thyroid gland.

Includes a description of the hormones secreted by the pituitary and hypothalamus that control the thyroid gland.

Includes a discussion about how thyroid hormones affect the body.

Includes a discussion about how thyroid hormones are regulated by negative feedback.

Includes information about at least 2 thyroid disorders.

Explanation / Answer

The lobules of thyroid is composed of about 20 to 40 dispersed follicles lined by cuboidal to low columnar epithelium.Thyroid gland also contain interfollicular cells called C-cells.

Harmones secreted by thyroid gland are thyroxine,triiodothyronine and calcitonin.The former two harmones are secreted by thyroid follicles.Thyroid follicular epithelial cells convert thyroglubulin into thyroxine(T4) and lesser amount of triiodothyronine(T3).The parafollicular cells or C-cells synthesizes and secrete calcitonin.

The secretion of the harmones from the thyroid is controlled by anterior pituitary by thyrotropin,while TSH secretion itself is regulated by TRH produced in hypothalamus.somatostatin from hypothalamus inhibits TSH secretion.

[ Anterior pituitary => TSH ==> Thyroid gland ==> T3 amd T4 ==>if in excess iinhibits anterior pituitary and hypothalamus.]

Hypothalamus==>TRH==>stimulate ant pituitary

THYROID harmones negative regulation-

Hypothalamus ==> SST ==>inhibits ant. Pituitary.==>regulates thyroid gland.

Thyroid harmone affect the function of practically every body cell.

1.Growth and development- essential for normal growth and development.

2.Metabolism- marked effect on lipid,carbohydrate and protein metabolism.

Lipids-enhance lipolysis,cholesterol metabolism (all phases) are accelerated.

Carbohydrates-it is stimulated.

Proteins-overall effect of T3 iis catabolic.

3.calorigenesis-they increase BMR by stimulation of cellular metabolism and resetting energy stat and are important for maintaining body temperature.

4.CVS-stimulatory effect on heart by direct action on contractile elements and by up regulation of adrenergic receptors.

5.Nervous system-have profound effect on mental growth.

6.It also help in maintaining skeletal muscle activity,haemopoeisis and reproduction.

Disorders caused by thyroid harmones imbalance includes thyrotoxicosis,goitre,myxedema,cretinism,graves disease etc

1.Thyrotoxicosis is hypermetabolic state caused by elevated levels of T3 and T4.It is referred as hyperthyroidism.The most common causes are- diffuse hyperplasia of thyroid gland,hyperfunctional multinodular goiter and hyperfunctional thyroid adenoma.

Clinical manifestations include soft,warm and flushed skin.Heat intolerance is common,weight loss,increased appetite,tachycardia,palpitations,cardiomegaly,anxiety,emotional lability,insomnia,wide-eyed and starring gaze,thyroid storm etc.

2.myxedema- hypothyroidism developing in adult or older childmIt is marked by slowing of physical and mental activity.The intial symptoms include generalized fatigue,apathy,mental sluggishness,cold intolerant ,frequently overweight etc.speech and intellectual functions are slowed,decreased sympathetic activity results in constipation and decreased sweating.skin is cool and pale and etc.

Measurement of serum TSH level is the most sensitive screening test for this disorder.

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