The hypothalamus releases TRH, which tells the pituitary to release TSH, which tells the thyroid to make T4 and T3. When T4 and T3 levels rise high enough, the hypothalamus shuts down TRH to stop the cascade. This negative feedback loop keeps thyroid hormones balanced.
Let's walk through the feedback loop for thyroid hormones. So this all starts in the brain with the hypothalamus here. The hypothalamus releases trh, which is called thyrotropin releasing hormone. Now TRH is then going to stimulate the anterior pituitary gland in the brain and that anterior pituitary, the ap, is going to release the thyroid stimulating hormone or the tsh. Now tsh, that's a really important one for you to know because that one is going to go to the thyroid gland and then the thyroid gland, because it was stimulated by tsh, it's going to release the thyroid hormones. These are the active thyroid hormones or T4 and T3. So the thyroid gland is going to release those. Then when there is enough T4 and T3 in the body, the brain, the hypothalamus sees that and it says, oh, okay, we're good here now. So it stops releasing trh. So the whole system stops. That's the feed.
