mmm what does your diet look like? and training 4-5 times a week for an hour and a half do you go to failure every set? meaning are you busting your ass at the gym every workout every set every time? may need a week off? i would talk to your doc, the stuff i brought up are the basics, but i am not a doc. ask him/her what could be the cause, assuming everything thing else in bloodwork was good my "guess" would be over training/diet with no drugs or booze used. take a week off eat right and get re tested, if you got a good doc he will be able to find a way so ins covers it..