A man's penis is not only a measure of his manhood, it can also be a harbinger for hidden health problems. In 80% of cases, erectile dysfunction (ED), the inability to obtain and sustain an erection, can be traced back to an organic cause not related to sexual drive.
This may come as a surprise, especially to teenage boys, but obtaining an erection is physiologically hard. Penile erection can only come about when the necessary psychological, neurological, vascular and hormonal factors are all aligned. Problems along the way can stymie a night of lovemaking and take its toll on self-esteem.