Hi ejb,
Well GH was only licensed for use in children with PWS relatively recently, and used to be started just before puberty. However in the USA they were using it younger and younger with great results, so we asked our endo if we could have a trial. DD2 was only 12 mths. Luckily the endo agreed (really put her professional neck on the block for us) and we started it at 14 mths.
We give her a nightly injection - it's a pen system like an insulin pen. Dead easy to use (twist to get the dose, push very fine needle into skin, then press top to deliver drug). She doesn't seem to feel it - I gave myself a stab one night to see how bad it was and you can hardly feel it.
DD was profoundly hypotonic - on oxygen for first year, NG fed, couldn't roll, had just started "sitting" at 12 mths, (ie could hold herself up if well propped up!), very very low tone. Predicted to sit at age 2ish, walk about 4ish (if that). We started GH at 14 mths and she crawled at 18 months (proper crawling), was off her NG at 18 months and walked (albeit VERY wobbly!) at 27 months. We have noticed a huge change in her physical appearance and composition (if that makes sense), in that she now has defined muscle visible in her arms and legs whereas before she was like a bag of jelly.
We really believe it's due to the GH. OK she still has GDD and has low tone compared to her peers but nothing like it was. We haven't seen any side effects and physiologically she is doing fine - no problems with her blood levels, bone growth is good, etc. She is reviewed regularly by endo who is very chuffed she took a chance for her (as we are!) and her general paed is gobsmacked.
Any more questions just shout. Sorry for the long post.