Hello and thanks for reading. Honestly, at 18 you are pretty much still peaking in terms of natural hormone production. There are so many factors that come into height and other bio-stats that it’s hard to tell where the origin of a particular trait comes from. It could be a genetic thing, for instance, if your parents/grandparents (and other descendants) had a similar height. Generally speaking, if you have normal muscle and bone growth/recovery then your HGH levels are fine. Height is just one factor that can be pre-programmed before you are even born, and out of your control.