RADIOISOTOPES — AEBERSOLD 233 



Such experiments clearly prove that our body processes are continu- 

 ally breaking clown and building up organic molecules. The breaking- 

 down process or degradation of complex molecules releases the energy 

 which is necessary for proper functioning of our bodies. It also fur- 

 nishes some of the less complex components of our tissue. A fine 

 balance is maintained between the degradation to obtain energy and 

 the synthesis to make new organic molecules for our body's needs. 



Radioisotopes are thus providing us with information not only on 

 how we "tick" when healthy but on what goes WTong in disease. By 

 comparing the behavior of isotope-labeled compounds in normal ani- 

 mals with their behavior in animals having diseases such as cirrhosis 

 of the liver or cancer, investigators are able to look for differences 

 which may give valuable leads as to the cause and cure of the disease. 



Another goal of this type of investigation would be to use the behav- 

 ior of the labeled compound for diagnosing such diseases. 



MEDICAL DIAGNOSIS 



In medical diagnosis radioisotopes have been used to determine 

 blood volumes ; blood circulation to the extremities ; pumping efficiency 

 of the heart ; thyroid-gland activity ; and the location of brain tumors. 



Radioisotopes have been used by many large hospitals and medical 

 centers for measuring the volume of blood in patients, especially those 

 scheduled for surgery. In this particular diagnostic test a portion of 

 the blood, the serum albumin, is labeled with a known concentration 

 of radioiodine and then injected into the patient. After the blood 

 has had a chance to circulate throughout the body, another blood sam- 

 ple is taken and the concentration redetermined. The amount of dilu- 

 tion that has taken place is a measure of the total volume of blood in 

 the patient. Even wounded United Nations troops in Korea have been 

 tested for loss of blood by radioisotope blood-volume determinations. 

 These same troops have also benefited from better methods of using 

 blood preservatives and plasma substitutes developed through tracer 

 studies. 



The most widely used diagnostic test, however, is the radioiodine 

 test for thyroid activity. The test is also simple. Radioactive iodine 

 in the simple compound, sodium iodide, is given to the patient by 

 mouth. It appears that the patient is simply drinking a glass of water. 



Practically all iodine, which is absorbed in the body, is taken up by 

 the thyroid gland. This is because of the gland's production of an 

 iodine containing hormone called thyroxine. If the gland is over- 

 active (hyperthyroidism), its production of thyroxine is large and 

 accordingly its ability to take up iodine is large. Underactivity of the 

 gland (hypothyroidism) produces the opposite effect. 



The radioactive iodine wnll also go to the thyroid, but since it gives 

 off penetrating gamma rays, its rate of uptake in the gland may be 



