Growth hormone resistance?

First post. In an attempt to raise my pre treatment IGF 1 of 120, I have had increasing doses of HGH to 2.4 ius twice a day, only to get an IGF 1 in the low 200s. It always starts higher then wanes. I think top of the range is about impossible for me. I am 50, and get HGH covered by insurance and get tested a lot. Interestingly, all of the hormrones I am prescribed go the same way. Seems to be some resistance.
I am interested in knowing if someone has had the same experience or knows why the IGF wouldn't be higher on 4.8 ius a day.
I have bad bones, nine bad discs, low IGF1, hence the HGH was prescribed.
Thanks.