The changes in you body as you grow are controlled by the chemical signals in the endocrine system called *

enzymes

reflexes

hormones

neurons

If I'm not mistaken the answer is hormones.

Explanation:

Hormones are chemical messengers that travel throughout the body coordinating complex processes like growth, metabolism, and fertility. They can influence the function of the immune system, and even alter behavior. Before birth, they guide development of the brain and reproductive system.