Well, like I said, I'm quoting informed opinion (not mine), and I am not a doctor or biologist, although I had an active interest in biology when I was young, and have read a lot. Hormones are messengers, and they also act on tissues. They are in fact required for proper functioning, and the informed opinion part comes from someone I know who does have a medical background and knows a great deal about endocrinology. I do think he's generally right, although in his mind he worries about those of us who transition, but he doesn't understand really what it's all about, either - how it can be necessary for a healthy life for a trans person.