GHRP can increase prolactin and cortisol levels, but GHRP6 is the safest of the all the GHRP with the least sides (also probably the weakest though in gh pulse release)
I've never heard of anyone getting prolactin gyno from GHRP6-you would have to be so sensitive that smelling deca or tren and you'd be leaking like a new mother
I find it hard to believe thats all he was using and got lactating prolactin gyno.
If you are concerned about it you can run an anti e with it as prolactin is problematic in the presence of estrogen, or can run bromo, caber or prami.
But i really think its unnecessary