The Efficacy and Safety of Creating a Rat Hypothyroidism Model Through Intramuscular Injection of 131 Iodine

The study investigated the use of intramuscular injection of sodium 131iodide (131I) to create a rat hypothyroidism model, challenging previous speculations that it would damage muscle tissue and fail to induce hypothyroidism. By injecting 0.25-1.00 mCi 131I into rat muscle, the researchers found that the iodine quickly diffused into the bloodstream and concentrated in the liver and thyroid, effectively reducing serum FT4 and FT3 levels in a dose-dependent manner. Importantly, there were no adverse effects such as hair loss, skin ulcers, or impaired leg mobility, and MRI signals showed no significant differences between 131I and saline injection sites. The study concluded that intramuscular injection of 131I at doses ≤1 mCi/0.2 mL is a safe and effective method for inducing hypothyroidism in rats without significant muscle or tissue damage.