The pituitary gland looks like a pea hanging by a stalk from the underside of the brain. It is very fragile, and if it gets damaged the body can be starved of vital hormones. There's a case study of a 14 year old boy who had 3 concussions that did not require medical attention, and then a fourth (playing soccer) that did, and afterwards he failed to grow, his strength and energy levels declined, and his schoolwork suffered. Once his missing hormones were replaced he grew normally again and regained his strength and energy. www.ncbi.nlm.nih.gov/pmc/articles/PMC1978466/ Pituitary damage after concussions is well documented in adults, less so in children. But I think most parents would like to be warned that this can happen, and that it can be treated. (And normal growth after injury is not necessarily a sign that you're out of the wood, as late onset can occur.)