The Efficacy and Safety of Making Rat Hypothyroidism Model through Intramuscular Injection of 131Iodine

Abstract Previously it was speculated that intramuscular injection of sodium 131iodide (131I) should not be utilized to make rat hypothyroidism model, because intramuscular 131I would destroy the neighboring muscle and fail to make hypothyroidism rat. Our experiments initially systematically rectify the speculation. After injecting 0.25-1.00 mCi 131I /0.2 mL into rat muscle between iliac crest and femur, 131I would quickly diffuse into vessels and concentrate in liver and thyroid basing on 131I SPECT/CT imaging. The decreased amplitude of serum FT4 and FT3 was related to the injected 131I dose and the time post injection. Around 131I injection loci there was no hair loss, skin ulcer or abnormal legs mobility. The MRI signals between 131I and normal saline injection loci were not different significantly. So intramuscular injection of 131I ≤1 mCi/0.2 mL could successfully make hypothyroidism rat model and would not significantly damage muscle, the neighboring bone marrow, skin and hair.