Many researchers are currently investigating the role isoflavones found in soy-based products play in improving human health.? Isoflavones are a class of phytoestrogens, that are found in greatest concentration within soybeans and other soy products.? The two main isoflavones, genistein and daidzein, have been identified to create a cholesterol-lowering effect.? The study sought to identify if this effect was correlated to small changes in thyroid hormones.? Thyroid hormones play an active role in every cell and organ within the body including: rate of metabolism, heartbeat, temperature, digestion and replacement of dying cells.? An excess of thyroid hormones within the body speeds these processes up too quickly, and too little, slows everything down.? Only genistein had minimal correlated with an increase in thyroid hormones, indicating no cholesterol-lowering effect due to thyroid hormones.? Despite this finding, both genistein and daidzein, a component in all soy products, were confirmed to lower cholesterol in a beneficial way, but utilized a non-thyroid hormone mechanism.