Hi, I Have A Question About A Disease I Just

Hi, i have a question about a disease i just heard of. I can't remember the name, however i know the symptons/facts, can you possibly tell me the name?
Basically, it's about missing a hormone in the brain, which results in your nerural pathways burns out, when aging. at age 5-6 the physical limitations start to show, skills already learnt years before.

i hope you can help me tell the name of it.