They work on two different parts of the same system, which is exactly why they're so often prescribed together: combined, they produce a stronger, cleaner, more physiologic release of GH than either one on its own
Also, because they have a selective diet
S., Liu, X., Cui, W., & Li, D
PloS One , 13 (6), e0198626
Typical Treatment Timeline First 12 Months Hair shedding may stabilize Hair growth cycle begins transitioning 34 Months Early improvements in thickness and density Reduced shedding 6 Months Noticeably fuller-looking hair for many patients 912 Months Continued improvement with consistent use Individual results vary and depend on factors such as age, genetics, hormone levels, nutrition, and treatment adherence
The Commercial Reality Timmermans points out why human studies remain elusive: The patent for BPC-157 expired long ago