Well, two things come to mind.
1) how much BF is still on your body?
2) I've seen and read about this - systemically our male society is losing testosterone dramatically from decade to decade. Used to be, men averaged around 700-900 well into their twenties, now it's around 450-650 w/ 550-600 being what a typical men's clinic would expect to see. Lot's of reason for this - and it's just as much to do with your ego, opinion of self & activities that determine your longterm T levels. I blame gradual, runaway feminism which created the effiminate male. It's probably a complicated system that makes up your lifestyle that is delivering the unimpressive T results. Do more manly things, stop masturbating & get enough essential minerals to have healthy T levels. You know, stuff like magnesium, sodium, iron, zinc, copper, etc.
Sleep makes a difference too. You could realistically alter those levels enough naturally to where you were closer to 700, which still isn't ideal but well enough.