OK, I thought a little and I looked it up in a book; primary amenorrhea-never had a period (think too young, genetic disorder,...); secondary amen.-pregnancy (#1 cause), thin athlete syndrome, stress, eating disorder, polycystic ovaries, uncontrolled endocrine disorder, drugs,...)
work-up: preg test, pelvic US, FSH, ...
this is a real complicated subject; thanks for the question, though, since I needed to review the subject; I work in an all male facility: state prison!