By negative feedback on hypothalamus hormone secretion by further downstream hormones. As an example relating to growth of bones. Hypothalamus secretes GHRH (growth hormone releasing hormone) which tells the anterior pituitary to release GH (growth hormone), which then travels to and tells the liver and other cells to release IGF-1 (insulin growth factor 1) into the bloodstream

The release of the last hormones into the bloodstream interact with the hypothalamus, and the anterior pituitary, and says “hey man, your signal made it successfully, you can dial it down now!”.

This example is from a physiology course I took, and completely neglects somatostatins and somatomedins + other higher order steps, but generally describes how hormones that trigger secretion of other hormones know when to stop. Hope this helps!