The Endocrine system regulates the activities of the body by secreting complex chemical substances (hormones) into the blood stream. These secretions come from a variety of glands which control various organs of the body.The Gonads Roots, suffixes, and prefixes Cancer Focus. Related Abbreviations and Acronyms Further Resources Functions of the Endocrine System. The Endocrine system (along with the nervous system) controls and regulates the complex activities of the body.
Because these cells have a separate embryological origin from the thyroid follicular cells, and because they secrete calcitonin, they in essence form a separate endocrine organ. (In some animals the C cells remain separate from the thyroid.) Calcitonin is secreted in response to high serum calcium concentrations, and it lowers the concentrations acutely by inhibiting.The fetal thyroid gland begins to function at about 12 weeks of gestation, and its function increases progressively thereafter. Within minutes after birth there is a sudden surge in thyrotropin secretion, followed by a marked increase in serum thyroxine and triiodothyronine concentrations.
Despite its importance the pituitary gland is no larger than a small pea. The Pituitary gland is made up of two separate glands: the Anterior lobe which is an outgrowth of the pharynx, and the Posterior lobe which is an outgrowth of the brain composed of neural (nerve) tissue.The remaining 80 percent of triiodothyronine comes from deiodination of thyroxine outside of the thyroid. Most if not all of the action of thyroid hormone in its target tissues is exerted by triiodothyronine.
Their actions and influence are so wide-ranging that vertebrates cannot live without them. Among other things, thyroid hormones specifically affect brain development; heart rate; lung function; blood function; bone growth; steroid hormone production and breakdown; sugar, fat, and protein breakdown; and some immune processes.Methimazole, 50 mg daily, depressed thyroxine synthesis (T4 10.5, free T4 2.5) and caused a rise in TSH to 11 U per ml. After discontinuation of treatment, TSH declined to 4.2 U per ml and chemical hyperthyroidism returned (T4 21.0 g per 100 ml, free T4 4.2, and total T3 475 ng per 100 ml.
The adrenal cortex is essential for life, as opposed to the adrenal medulla which is important but not indispensable. The anterior pituitary controls the adrenal cortex by secreting the hormone ACTH.In turn, the thyroid hormones inhibit the production and secretion of both thyrotropin-releasing hormone and thyrotropin. Decreased production of thyroid hormone results in increased thyrotropin secretion and thus increased thyroid hormone secretion.
Deciphering how endocrine disrupting compounds influence thyroid hormones is important due to their essential role in vertebrate brain development and energy-sustaining functions. Many environmental compounds, including the pesticides 2,4-D and DDD and the industrial chemicals PCBs and dioxins, interfere with thyroid hormone processes (Howdeshell 2002).Therefore, thyroxine may be considered a circulating precursor of triiodothyronine. In serum more than 99 percent of the thyroxine and triiodothyronine is bound to one of three proteins. These binding proteins are known as thyroxine-binding globulin, transthyretin (thyroxine-binding prealbumin and albumin.
The Anterior Lobe of the pituitary plays the 'master' role secreting six major hormones that affect most of the body, including the other Endocrine glands: ACTH (Adrenocorticotrophic hormone) stimulates the adrenal glands to secrete its hormones.Insulin also promotes the storage of glycogen in the liver. The Adrenal Glands The adrenal glands resemble small caps perched on top of each kidney. The Adrenal is actually a combination of two glands the adrenal cortex and the adrenal medulla.
He had measurable serum thyroid-stimulating hormone (TSH) levels (average 5.5 U per ml and the thyroxine-binding proteins, hearing, and epiphyseal structures were normal. There was no parental consanguinity nor were there thyroid abnormalities either in the parents or six siblings.The unusual sensitivity of the pituitary cells to TRH in spite of the markedly elevated serum thyroid hormone levels also suggested that the pituitary was insensitive to suppression by T3 or T4.
Thyrotropin-releasing hormone (TRH 200 g i.v., caused a brisk rise in TSH to 28 U per ml, with T4 rising to 28 g per 100 ml, free T4 to 5.6, and T3 to 730 ng per 100 ml, thus indicating that the pituitary-thyroid system was intact and that the patient's TSH was biologically active.Testosterone is the masculizing hormone inducing male secondary sexual characteristics after puberty. Female ovaries are two almond shaped glands on each side of the uterus. They have three main functions; (i) Containing immature ova (eggs (ii) The secretion of oestrogen, and (ii) the secretion of progesterone.
CAPTION : The two most active thyroid hormones, triiodothyronine (T3) (left) and thyroxine (T33) (right contain iodine atoms typical of the thyroid hormones. (click each image for 3-D interactive animation) CREDIT : ChemIDPlus, National Library of Medicine.About Hormones Hormones are secreted from the glands of the endocrine system, they are specific in that each hormone causes a response in a specific target organ or group of cells, rather than on the body as a whole.