The Thyroid Hormone Receptor (TR) is a protein that binds to thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3). These receptors are found in various tissues throughout the body and play a crucial role in regulating metabolism, growth, and development. When thyroid hormones attach to TRs, they influence gene expression, leading to various physiological effects. TRs are part of a larger family of nuclear hormone receptors, which also includes receptors for other hormones like steroids and retinoids. The activity of TRs can be affected by different factors, including the presence of co-regulators and the specific type of thyroid hormone bound. This regulation is essential for maintaining overall health and metabolic balance.