At 7 to 8 months post injury, the rate of pituitary dysfunction is very low. 5% to 27% depending on the study. The study also includes mild, moderate and severe TBI. Only 16% of mild TBI were tested with hypopituitarism in the one popular study. The prevalence in severe TBI was double that.

You also miss the point that the numbers for hypopituitarism consist of HGH, T and some others. The studies do no accurately differentiate between T and HGH. They do suggest that HGH should not be considered until a year post injury. Besides, HGH is expensive and often a lifelong therapy.