PROBLEM 6. Hormones Help Regulate Cell Activities 



249 



Goiter cases 



BMB 13-30 cases per 1000 

 \///////A 5-15 cases per 1000 

 I I 0-5 cases per 1000 



Iodine in water 



0-0.5 parts per billion 



V/////X Q-2 parts per billion 

 ] 2-20 parts per billion 



Fig. 241 Goiter ?nap of the United States showing co?iditio7is in 192^. Examine the 

 figures just above. What conclusions can you draw about the cause of siynple goiter? 

 Where were cases most commoji? Where were they least covmion? 



It may surprise you to learn that an 

 enlarged thyroid gland may mean that 

 the gland is secreting too little thyroxin. 

 You may have noticed that some people 

 have a swelling in the neck in the region 

 of the gland. They have a simple goiter. 

 These goiters may occur when there is 

 too little iodine in the diet. They are 

 thus more common in regions where the 

 amount of iodine salts in drinking water 

 or in near-by farm products is too small. 

 Health officers in such localities some- 

 times add iodine salts to the drinkiuCT 

 water. Sometimes the use of iodized 

 table salt is recommended. 



A different type of goiter. In a very dif- 

 ferent kind of enlarged gland or goiter 

 the gland produces too much thyroxin. 

 With oversecretion the rate of oxidation 

 increases. The person is often restless 

 and easily excited. In more severe cases, 



the patient loses weight, the temperature 

 is above normal, and the heart beats 

 more quickly than usual. This type of 

 goiter {exophthalmic goiter) sometimes 

 causes the eyes to bulge. It may become 

 serious, unless the amount of thyroxin 

 is reduced. This may be done by operat- 

 ing to remove a portion of the gland or 

 to shut off part of the blood supply to 

 the gland. To test your understanding 

 of the last paragraph do Exercise 2. 



An important discovery. There is a new 

 and interesting treatment for overactivity 

 of the thyroid gland. To understand it 

 you must stop for a moment to examine 

 an important discovery about atoms made 

 in recent years. It has been learned that 

 an element such as iodine, for example, 

 may have atoms of two or more kinds 

 which differ slightly even though they 

 are still atoms of iodine. Such atoms are 



