When people think of hormones they don’t know of the one that produces the most power. It is the Thyroid. There is a gland over the voice box that makes it. Not much is made in a year, so it has to be saved and used carefully. The total amount is about a couple teaspoons. Here is its mission. It drives the engines in each of 73 trillion cells in your body. And on top of that, it keeps all those engines, mitochondria, running at the same speed. That is important. Consider a train with 500 cars of heavy freight. Now add 6 engines and space them through the train. Now, you see each engine must be the same speed of each other engine or big big trouble. How do you yoke the engines together from cell to cell? Yep, thyroid hormone.