Parathyroid Gland

Parathyroid gland

   

    There are four parathyroid glands. They are small, light-colored lumps that stick out from the surface of the thyroid gland. All four glands are located on the thyroid gland.

They are butterfly-shaped and located inside the neck, more specifically on both sides of the windpipe.

   One of the parathyroid glands most important functions is to regulate the body's calcium and phosphorus levels. Another function of the parathyroid glands is to secrete parathyroid hormone, which causes the release of the calcium present in bone to extracellular fluid.

PTH does this by depressing the production of osteoblasts, special cells of the body involved in the production of bone and activating osteoclasts, other specialized cells involved in the removal of bone.

Receptors bind a specific hormone and the result is a specific physiologic response, meaning a normal response of the body.

    PTH finds its major target cells in bone, kidneys, and the gastrointestinal system.

Calcitonin, a hormone produced by the thyroid gland that also regulates ECF calcium levels and serves to counteract the calcium-producing effects of PTH.

    The adult body contains as much as 1 kg of calcium. Most of this calcium is found in bone and teeth. The four parathyroid glands secrete the parathyroid hormone (PTH). It opposes the effect of thyrocalcitonin. It does this by removing calcium from its storage sites in bones, releasing it into the bloodstream. It also signals the kidneys to reabsorb more of this mineral, transporting it into the blood. It also signals the small intestine to absorb more of this mineral, transporting it from the diet into the blood.

    Calcium is important for steps of body metabolism. Blood cannot clot without sufficient calcium. Skeletal muscles require this mineral in order to contract. A deficiency of PTH can lead to tetany, muscle weakness due to lack of available calcium in the blood.

Sumber : Bpk. Dr. Iskandar Zulkarnain

#posting tugas cyberprenership

    ahmad baihaqi

    NIM 1112503964

Thyroid System

    Iodine deficient goiter, (enlargement of the thyroid gland) results because iodine is a crucial component of active thyroid hormones. If there is a low level of iodine in the diet, then less active T3 and T4 can be synthesized. As diagrammed in the figure, when there is less T3 and T4, there is reduced negative feedback inhibition on secretion of the tropic hormones, TRH (thyrotropin releasing hormone; released by the hypothalamus) and TSH (thyroid stimulating hormone or thyrotropin; released by the anterior pituitary). TSH stimulates all aspects of thyroid hormone synthesis; it also stimulates proliferation of follicle cells. When iodine in the diet is low but not too low, individuals may have goiter and yet be euthyroid, because the enlarged thyroid gland is better able to use the limited amount of iodine available. This is an example of hormonal homeostasis.

 

    Graves disease is the most common cause of hyperthyroidism. Graves disease is an autoimmune disorder in which antibodies are produced that bind to the TSH receptor. Instead of destroying the receptor, these antibodies activate it, stimulating synthesis of T3 and T4, and causing growth of the thyroid gland. Negative feedback inhibition is increased, so the levels of TRH and TSH decrease, but this does not decrease thyroid hormone production because the stimulation of the thyroid gland is independent of TSH. Measurement of low TSH levels is a key diagnostic test for hyperthyroidism

Sumber : Bpk. Dr. Iskandar Zulkarnain

#posting tugas cyberprenership

    ahmad baihaqi

    NIM 1112503964

The Thyroid gland

   The Thyroid gland

     The Thyroid gland is one of the largest endocrine glands in the body. It is positioned on the neck just below the Larynx and has two lobes with one on either side of the trachea. It is involved in the production of the hormones T3 (triiodothyronine) and T4 (thyroxine). These hormones increase the metabolic activity of the body‘s cells. The thyroid also produces and releases the hormone calcitonin (thyrocalcitonin) which contributes to the regulation of blood calcium levels. Thyrocalcitonin or calcitonin decreases the concentration of calcium in the blood. Most of the calcium removed from the blood is stored in the bones.

   The thyroid hormone consists of two components, thyroxine and iodine. This hormone increases the metabolism of most body cells. A deficiency of iodine in the diet leads to the enlargement of the thyroid gland, known as a simple goiter. Hypothyroidism during early development leads to cretinism. In adults, it produces myxedema, characterized by obesity and lethargy. Hyperthyroidism leads to a condition known as exophthalmic goiter, characterized by weight loss as well as hyperactive and irritable behavior.

The thyroid gland is a two-lobed gland that manifests a remarkably powerful active transport mechanism for up-taking iodide ions from the blood.

    As blood flows through the gland, iodide is converted to an active form of iodine. This iodine combines with an amino acid called tyrosine. Two molecules of iodinated tyrosine then combine to form thryroxine. Following its formation, the thyroxine becomes bound to a polysaccharide-protein material called thyroglobulin. The normal thyroid gland may store several weeks supply of thyroxine in this bound form. An enzymatic splitting of the thyroxine from the thyroglobulin occurs when a specific hormone is released into the blood.

   This hormone, produced by the pituitary gland, is known as thyroid-stimulating hormone (TSH). TSH stimulates certain major rate-limiting steps in thyroxine secretion, and thereby alters its rate of release. A variety of bodily defects, either dietary, hereditary, or disease induced, may decrease the amount of thyroxine released into the blood.

   Thyroxine serves to stimulate oxidative metabolism in cells; it increases the oxygen consumption and heat production of most body tissues, a notable exception being the brain. Thyroxine is also necessary for normal growth. The most likely explanation being that thyroxine promotes the effects of growth hormone on protein synthesis. The absence of thyroxine significantly reduces the ability of growth hormone to stimulate amino acid uptake and RNA synthesis. Thyroxine also plays a crucial role in the closely related area of organ development, particularly that of the central nervous system.

   If there is an insufficient amount of thyroxine, a condition referred to as hypothyroidism results. Symptoms of hypothyroidism stem from the fact that there is a reduction in the rate of oxidative energy-releasing reactions within the body cells. Usually the patient shows puffy skin, sluggishness, and lowered vitality. Other symptoms of hypothyroidism include weight gain, decreased libido, inability to tolerate cold, muscle pain and spasm, insomnia and brittle nails. 

Sumber : Bpk. Dr. Iskandar Zulkarnain

#posting tugas cyberprenership

    ahmad baihaqi

    NIM 1112503964