Previous research had shown that administering thyroid hormones can speed metabolism, lower cholesterol levels and bolster weight loss. But unwanted side effects, particularly rapid heartbeats, often accompany the procedure. Gary Grover of Bristol-Myers Squibb and his colleagues investigated the two hormone receptors involved in mediating these effects, TR-beta and TR-alpha. They found that mice lacking the TR-alpha receptor experienced a much smaller heartbeat increase than control animals did in response to thyroid hormones. The other effects, such as lowered cholesterol and increased metabolism were similar between both groups.
The team next administered a chemical known as KB-141, which stimulates only TR-beta, to normal mice, rats and monkeys. Animals in all three groups exhibited decreased cholesterol levels and weight loss without increased heart rate. Although the findings are very preliminary, the authors conclude that KB-141 and related compounds "may offer several types of therapeutic potential and are candidates for further exploration."