When to begin growth hormone treatment for short stature.?

At puberty. At puberty, because their is synergy between reproductive hormones and hgh. Also, the growth plates are open.
When/if criteria met. This is best determined by the pediatric endocrinologist involved in the case. Whether it is used as replacement for deficiency, or in a short course to push a delayed puberty, the decision is complex.I deficiency cases it is timed to help establish growth in natural puberty.In kids with normal varient familial short stature, it may or may not offer any increase in final height.