If it is related to thinness, it is mainly because thyroxine accelerates the decomposition of protein and the synthesis of protein can't keep up, so people are thin. This is caused by excessive secretion of thyroxine, which will lead to hyperthyroidism, which is hyperthyroidism.

Others will accelerate the metabolism of sugar and fat.

In fact, different amounts of thyroxine have completely different effects.

If the child is thin and smart, it should have nothing to do with thyroxine.

Most adults lose weight when they are hyperthyroidism.

There should be thyroxine to turn tadpoles into frogs, because thyroxine can promote growth and development. It is different from growth hormone and higher than growth hormone, mainly because of its effect on other sex hormones.

This is just my comprehensive view based on what I have learned, which is slightly less detailed. I will make it up in detail when I have the opportunity.