definitions - understudies. understudy (n.) 1.someone who takes the place of another (as when things get dangerous or difficult)the star had a stand-in for dangerous scenes we need extra employees for summer fill-ins. 2.an actor able to replace a regular performer when required. understudy (v.)
Radiation can come in the form of a pill. Iodine (131 I) used in thyroid treatment might be given in pill form or as a liquid. The choice is an institutional decision based on many factors, including the amount to be given to a patient.
Most thyroid pills have a half life of 6.7 days which means they must be stopped for four to five weeks (five half lives) before accurate thyroid testing is possible. An exception to the long half life of thyroid medication is Cytomel - a thyroid pill with a half life of only forty-eight hours.