And what causes this pituitary gland to release TSH is the hypothalamus releasing our TRH. So we have a positive feedback loop going this way, a positive feedback loop going this way. But when we begin to increase the concentration of T three and T four, that will basically inhibit the release of TRH by the hypothalamus and the release of TSH, the thyroid stimulating hormone, by then to hear a pituitary gland. So we have a negative feedback mechanism that basically helps us control the levels of T three and T four in our body. So basically, if we have a very low level of T three and T four, that will basically cause the hypothalamus to release TRH, which will cause the anterior pituitary gland to release TSH, which will go on and cause the thyroid to release these two hormones. But over time, as the concentration in the blood plasma of T three and T four increases, that will basically affect these two structures via a negative feedback loop, it will cause it will inhibit them from releasing these hormones.