Now, there are two types of cells that we're going to discuss in just a moment that are responsible for producing three types of hormones. We have T three, also known as the triadothyrene hormone. We have the T four, also known as the thyroxine hormone, and we have our calcitonin. Now, T three and T four hormones of the thyroid gland are actually controlled and stimulated by a hormone that is produced by our anterior pituitary gland known as the thyroid stimulating hormone or TSH. And TSH itself is stimulating controlled by TRH, the thyroid releasing hormone produced by the hypothalamus. So we have this positive feedback mechanism that allows us to basically control the production and release of T three and T four.