Question

what would happen if there were no negative feedback control on growth hormone and thyroid hormone?

Answer 1

Negative feedback allows the body to know when enough of a hormone (or anything that can be measured) has been used. Without negative feedback, the brain cannot tell when it has secreted growth hormone releasing hormone (the brain uses negative feedback from growth hormone to know that it was successful in releasing GHRH). The same goes for the brain and thyrotropin releasing hormone.

Without negative feedback on these hormones you will grow uncontrolled and your metabolism (as well as body temp) will spiral out of control. Also, yes if this happened to someone it is highly unlikely they would survive.