First apply Minoxidil. Use 10-20 drops in both needy and normal appearing areas, twice/day for the first two months then once/day. Work it in with a hairbrush or micro needle roller.
Most probably you have a androgenetic type hair
loss. I dont advice to use finasteride because of
possible side effects and being under
the necessity of using that chemical for almost life long to stop hair
loss.You may start to use minoxidil %5 to thicken the crown area and stop hair...
As men mature often their juvenile hairline may recede a little bit. From the picture your hairline appears appropriate for the male aesthetic, however this is best determined by personal preference and a professional evaluation to find whether or not miniaturization exists....
