In my opinion, This is wrong, i am nearly 33 years old and have the nearly same pattern of the 17 years old patient, but still waiting for my 37-38 to get a hair-transplant.There is always a risk, to go to nw6 even after 40 years old, i believe the best bet to minimize this risk to wait until you age over to mid-late 30s in my type of (diffusion all over the scalp,nw3).it is your own choice to use any meds, which i dont, for even a 17 years old, i believe even meds should take with precaution with a doctor's prescribe.
I am sorry to say this Dr.Mohebi but all with respect to you,in my opinion, I believe this is unethical to make a hairtransplant under-18 patient with mpb.
Even if the patient is on Meds,he may get the sides in the following years or he may want to quit meds because it got boring there is a chance even meds can stop to work for anyone , got enough hair for a second or a third round?, this is human nature, even if his family tree had show no hairloss at all,i believe it is impossible to give a point-blank decision for this young fella to not get further aggressive hairloss.