Goitrogens-anti Thyroid Agents

GOITROGENS-ANTI THYROID AGENTS



Iodine is an essential micro nutrient for all animal species & iodine deficiency is among the most prevelent nutritional problem in many developing countries .

In 1928 Chesney & his collegues at Johns Hopkin Hospital made the chance observation that rabbits raised in the laboratory for the study of Syphilis & fed largely on Cabbage developed Goiter .Thsi observation was followed up by Charles Hercus & his collegue in New Zealand .They established the goitrogenic properties of Cabbage , Turnip & particularly the seeds of Cabbage , Mustard & Rye. A large number of food stuffs possess anti-thyroid agents collectively designated as Goitrogens.

Depending upon the level of interference the goitrogens have been caategorized into three classes.

CLASS 1 GOITROGENS : Are those which inhibit the Iodine uptake by Thyroid gland.These are Thiocynate , Isothiocynate & cyanogenic glucosides.

CLASS 2 GOITROGENS :Are those which affect the stages of Organification & coupling in the process of Thyroxine synthesis.These are Thiourea & Flavonoides.

CLASS 3 GOITROGENS :Are those which interfere at the stage of Proteolysis-a step necessary for utilization of Thyroxine.These are Iodine itself when it is in excess & lithium.


In Sudan endemic Goiter & Iodine deficiency disorders are serious health problems.In these areas Iodine deficiency was identified as the principal etilogic factor.However consumption of Pearl Millet ( Bajra ) was suggested as an instrumental factor in the etiology of Endemic Goiter in Western Sudan.Pearl millet or Bajra is the main source of food energy for the rural people in many areas of semiarid tropics.Studies showed that the goitrogenic substance was present in both bran & endosperm portions of the grain & was not destroyed by grain fermentation however autoclaving reduced the goitrogeic properties of Pearl Millet.The Goitrogenic substances present in Pearl Millet are Glycosyl Vitexin , Glycosyl Orientin & Vitexin.

Sorghum( Jowar ) like Pearl Millet ( Bajra ) also contains goitrogenic substance .The goitrogen in Sorghum is known as Dhurin.
Casava is cultivated extensively in developing countries & represents an essential dietary source of energy for more than 200 million people in the tropics.Casava has been demonstrated in the etiology of endemic Goiter & endemic Cretinism in Zaire.Casava containd Linamarin which is groitrogenic substance.The proper processing of Casava-drying , soakig in water , rinsingor baking effectively reduces Casava's Linamarin content. Vegtables from Cruciferae family like Cabbage , Brocoli , Turnip etc also contain goitrogens.However with heating they get destroyed.Soya bean even the processed ones have anti thyroid properties.Genistein & Daizein are much touted for their health benefits but what isunpublicized is they are anti-thyroid agents.Therefore individuals who consume Soyabean products habitually may encounter thyroid disturbances.

Thus foods containing goitrogens should not be eaten regularly or in large amounts without adequate processing .However the same foods can be used in the treatmen of hperthyroidism.

ARTICLE BY ,
DIETICIAN MOKSHA