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Definition of Iodine-125
1. Noun. Light radioactive isotope of iodine with a half-life of 60 days; used as a tracer in thyroid studies and as a treatment for hyperthyroidism. 
Medical Definition of Iodine-125
1. 
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1. Noun. Light radioactive isotope of iodine with a half-life of 60 days; used as a tracer in thyroid studies and as a treatment for hyperthyroidism. 
1.