Many cause of hair loss.  Genetics, lifestyle, etc.  Mine started thinning long ago and I am actually scared to try preventive methods after reading all those Yun Nam scam stuff.

I tried a few methods to control it but so far only two worked.
Method 1:  Some supplements for regrow hair bought by my wife's Thai colleague from Thai.  But after the colleague stopped working together, I have no source of this supplement, so had to stop.

Method 2:  Essential oil combination of Rosemary and Cedarwood massaged onto the scalp.  My wife tried this on me, I was very sceptical at first, but since I had nothing to lose, I let her go ahead.  Seems like my hair is now thicker and less seeing scalp.  I regret not taking before- and after pics because I was so sceptical.