Why Does Radioactive Iodine Decrease Faster in Some Bodies?

[alara_rc]

thanx for help in advance,

we know that radioactive iodine is given to people to minimize their thyroid growth or plain thyroid activity. This certain iodine 131-53 I, has a half life of 7.56 days. so why would the radiation in the human body decrease at a faster rate than at the calculated rate?

 

[CRGreathouse]

Because the body excretes iodine, so the 131I is lost through both decay and excretion. Google for "biological half-life".