Low sex drive has nothing do with sexual function, but more the actual desire to participate. As someone who knows from first hand experience, low testosterone will definitely have this effect and as not, few other immediate symptoms. Just because a man produces enough testosterone, other factors such as high estradiol prevents it from being utilized. Result- low sex drive. A simple blood test can reveal it. As high as 20% of men have some part of the condition. It only takes a slight imbalance to have an effect. The long term effects of not correcting the problem makes it more than worth the effort to find out. A very low testosterone condition will make it difficult to maintain an erection...which in itself subdues the drive. It's not always a mental thing. Chemicals - especially the ones the body produces - can make HUGE mental impacts.