29 and not balding yet

Can you have a sensitivity to DHT and not have signs of MPB nor history of it.  Does that mean that I never have to worry?  Can I start testosterone therapy now?

Maybe you don’t have the genetics for balding, but some men who have it may not show it until a later age.  I have seen it appear in at least one 50 year old man.  If you go on testosterone, you might precipitate the genetics if you have the genes.  If you don’t have the genes for balding, then taking testosterone will not cause hair loss