Best Known
Antithyroid Substances – The Three Best Known Antithyroid Drugs
Drugs that are known to inhibit the secretion of thyroid hormones are generally known as antithyroid substances. Three of the best known antithyroid substances are propylthiouracil, thiocyanate, and inorganic iodides. Each of this drugs blocks thyroid secretion in a different way and the different mechanisms by which they do so are further explained.
Propylthiouracil
Propylthiouracil — and its relatives, methimazole and carbimazole — decrease thyroid hormone formation by preventing its formation from iodides and tyrosine. This drug acts by blocking the peroxidase enzyme that is necessary in the first step of the formation of thyroid hormones, which is the oxidation of iodine so it can combine to tyrosine. Propylthiouracil also blocks the coupling of two iodinated tyrosines that are needed to form thyroxine or triiodothyronine, the two kinds of thyroid hormone.
Propylthiouracil does not prevent the formation of thyroglobulin. Since it only blocks the formation of thyroxine and triiodothyronine, the absence of both in the thyroglobulin can stimulate the pituitary gland to secrete more thyroid-stimulating hormone. This then promotes the growth of glandular tissue despite its being unable to produce the two hormones and forms a goiter..
Thiocyanate
Thiocyanate ions decrease iodide trapping, the mechanism by which the thyroid gland acquires iodine from the circulating blood. The same pump that transports the iodide ions necessary for normal thyroid function can also pump thiocyanate ions, perchlorate ions, and nitrate ions. Increased concentrations of thiocyanate ions then compete with the transport of iodide ions into the thyroid cells.
Like propylthiouracil, the decreased availability of iodide does not stop the formation of thyroglobulin. Thiocyanate can only prevent the iodination of thyroglobulin and in consequence, prevents the formation of thyroid hormones.
As with propylthiouracil, when the pituitary gland senses a decrease in the concentrations of thyroxine and triiodothyronine, it secretes more TSH. The higher levels of TSH then causes overgrowth of the thyroid gland but still, the gland fails to produce enough amounts of hormone. This leads to the formation of an enlarged thyroid gland, also known as goiter.
Inorganic Iodides
Inorganic iodides inhibit most of the activities only when in very high concentrations, as in 100 times the normal plasma levels of iodides. This effect, however, remains only for a few weeks.
This inhibitory effect of iodides on the thyroid gland is due to the reduction in the rate of iodide trapping of the gland, which also decreases the rate of production of thyroxine and triiodothyronine. Even more so, the normal endocytosis of colloid from the follicles by the thyroid glandular cells is paralyzed in the face of extremely high iodide concentrations. As this is the first step in the release of thyroid hormones, thyroid hormone secretion is shut down almost immediately.
The mechanisms by which inorganic iodides work on the thyroid gland decreases the size of the thyroid and its blood supply due to its inactivity. This is the opposite of the previous two drugs, which only serve to increase the size of the gland.
Propylthiouracil and Iodides in Thyroidectomy
Hyperthyroid patients must undergo several weeks of preparation before going under the knife. It was found that these procedures could spell the difference between life and death for a patient and patient mortality has been greatly reduced since the development of these preoperative procedures.
Several weeks prior to the operation, the patient is administered with the antithyroid substance propylthiouracil until such time that the basal metabolic rate of the patient reaches normal levels. One to two weeks before the operation, the patient receives high doses of iodides, which causes the gland to recede in size and its blood supply to diminish. This is done to decrease the necessary amount of surgery — an enlarged thyroid means a larger cut — and to decrease the amount of bleeding.
Top rated Thyroid Product Reviews
Diagnosing Thyroid Problems
About the Author
Battleship Trailer 2012 Rihanna movie
|
|
Errol Flynn Photo Mugs ERROL FLYNN (1909 – 1959) Irish-American film actor, best known for his swashbuckling roles …. |
|
|
A A Milne/cig Card Photo Mugs A A MILNE the English author, best known for Winnie the Pooh (1926) and The House at Pooh Corner (1928)…. |
|
|
Admiral Edward Hawke, First Baron Hawke (1710-81) Photo Mugs Hawke is best known for his defeat of the French fleet in Quiberon Bay in November 1759 – an extremely hazardous action fought close in on a rocky coast, in the fading light of a November evening….. |
|
|
The Famous Authors Series – William Shakespeare [VHS] $3.47 … |
|
|
Chicken Ranch (America’s Best-known Legalized Brothel) … |
|
|
World’s Best Known Dicks [VHS] $9.95 … |
|
|
Sunforce 50022 5-Watt Solar Battery Trickle Charger $49.95 Solar Power Chargers for your 12V batteries and accessories. Power-up anywhere, affordably! These Solar Power devices grab free “juice” from the sun! They extend the life of your 12V batteries, maintain the charge and allow you to run various electronics (deer feeders, landscaping pumps, etc.) from your batteries. Clean, silent operation… with both cigarette lighter adapter and battery clamps. T… |
|
|
Sunforce 50013 1-Watt Motorcycle and Powersports Solar Battery Charger $24.95 Never again worry about dead batteries on your Motorcycle, Personal Water Craft, ATVs, Snowmobiles, etc with the Sunforce Products 50013 Solar Powered 12V Sports Charger. The Sports Charger will charge any 12V battery with the power of the sun. The integr… |
|
|
Sunforce 50033 15-Watt Solar Charging Kit $94.95 Works with Automobiles/Boats/Tractors/ATVs/Electric Fences/Deer Feeders/Telemetry and More. Maintenance Free / Easy Installation. Pre Cut Holes for Easy Installation. 4 Stainless Steel Screws. Battery Clamps. CLA Adapter. 12ft Wire. 7 Amp Charge Controller. Works in All Weather Conditions. Ultra Bright Blue LED Provides Charging Indication. Built-in Blocking Diode Protects Battery Discha… |
|
|
Ferris Bueller’s Day Off $2.99 … |
Tags: best known, best known brands, best known classical music, best known quotes, best known songs, design, inspiration, portfolio, software, tools
This entry was posted on Saturday, February 7th, 2009 at 12:03 am and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.