COORDINATION 



443 



mal level, and subsequently all symptoms 

 of the disease disappear. Sometimes in sur- 

 gery too much of an overactive gland is 

 removed and the patient may then find 

 that he is suffering from myxedema and 

 must take thyroxin all the rest of his life. 

 Fortunately, the digestive enzymes have no 

 effect on thyroid extract, thyroxin, or even 

 the dried gland in contrast to insulin, a fact 

 which permits administration by mouth, an 

 important detail in the treatment of any 

 disease. 



Fifty years ago the presence of an un- 

 sightly enlarged thyroid was very common- 

 place in certain parts of the world. Sur- 

 prisingly, these regions were rather well- 

 defined and in them even the domestic ani- 

 mals had goiters. An examination of the soil 

 and water showed that there was a marked 

 deficiency of iodine. Along with this dis- 

 covery, the thyroid secretion was found 

 to be remarkably rich in iodine; it was not 

 difficult to fit the two together and con- 

 clude that goiter appeared in regions where 

 there was very little iodine available in the 

 food products and water. These areas were 

 spotted over the world. In the United States 

 they are concentrated along the St. Law- 

 rence River and Great Lakes regions. For 

 example, in 1924, 36 per cent of the school 

 children in Detroit showed incipient en- 

 demic goiter, but within 7 years after the 

 addition of potassium iodide to table salt 

 the incidence had dropped to 3 per cent. 

 In view of this experience, it has been pro- 

 posed that the word salt be legally recog- 

 nized in Michigan as iodized salt and that 

 the sale of any other salt in food stores be 

 prohibited. 



The presence of a goiter does not neces- 

 sarily mean that tlie gland is under- or over- 

 active. It does mean, however, that there is 

 some sort of disturbance in the thyroid 

 output. It may be compensating for the 

 lack of iodine and does this by producing 

 more thyroid tissue in an effort to supply 

 sufficient thyroxin to keep the body at a 

 normal basal metabolic level. Such com- 



pensating action is not uncommon in other 

 parts of the body, for example, an enlarged 

 heart muscle. If the thyroid cannot main- 

 tain a normal level of thyroxin, myxedema- 

 tous symptoms may be evident. If it can 

 supply the proper amount there are no 

 symptoms of the disease, although the indi- 

 vidual harbors the greatly enlarged gland 

 on the front of his neck which is at least 

 inconvenient, if not embarrassing. 



Overactivity. For some unknown reason, 

 the thyroid sometimes begins sponta- 

 neously to produce more thyroxin than the 

 body needs, and this may be accompanied 

 by a slight enlargement of the gland. It 

 differs from the simple goiter described 

 above because while it may not be en- 

 larged, or only slightly so, its output is 

 far greater. Obviously, abnormally high 

 amounts of hormone in the blood stream 

 increase the rate of burning foods (30 per 

 cent or more) and speed up all tlie bodily 

 activities. More food is consumed, yet there 

 is a wasting away of the body. Profuse 

 sweating occurs, the heart is overworked, 

 and external heat cannot be tolerated. All 

 this step-up produces a highly irritable and 

 nervous individual who is continually on 

 the move but accomplishing very little. The 

 action is like running an automobile at top 

 speed with the brakes set. It is clear that 

 such activity will soon result in the de- 

 struction of the organism itself. 



The control of such a condition, which is 

 called exophthalmic (from the fact that it 

 sometimes causes the eyes to bulge out of 

 their sockets) or toxic goiter, is by destroy- 

 ing a part of the cells that produce the 

 hormone ( Fig. 16-33 ) . This is easily accom- 

 plished by surgery and such operations are 

 very successful. In this age of the atom a 

 new method has been discovered which is 

 sometimes employed when for some reason 

 or other it is inadvisable to operate. It is the 

 use of radioactive iodine. Iodine, when sub- 

 jected to atomic radiations, becomes radio- 

 active itself. Such a form is called an iso- 

 tope. Since the thyroid picks up about 80 



