Amenorrhea This means the absence of menstruation. In pregnant women and postmenopausal women, this is normal. However, in women of childbearing age, this calls for medical concerns. Amenorrhea could be primary or secondary When it's primary, it means a young girl has not seen her first period (monarche) by age 16 years. If at 13 years, menses have not come, it is advised to start seeking medical attention immediately. It could be caused by; -Anatomic abnormalities like imperforate hymen -generic factors -Ovarian insufficiency -Delay in pituitary gland maturation, etc Secondary amenorrhea happens when menarche has occurred, but for some reason, the period abruptly ceases and could last for 3 months or more. This can be caused by -Thyroid disorder -Ovarian cyst -Hyperprolactinemia, stress, weight loss etc.