What is Amenorrhea? Amenorrhea is the clinical term for the absence of menstruation in women of reproductive age. It is officially defined as missing one or more menstrual periods. Primary Amenorrhea: When a young woman has not started her first menstrual period by age 15. Secondary Amenorrhea: The most common type. This occurs when a woman who has previously had regular menstrual cycles misses at least three periods in a row. While the absolute most common cause of secondary amenorrhea is a natural pregnancy, it can also act as an important warning sign indicating underlying problems with the reproductive organs, the endocrine system, or overall hormonal regulation. Symptoms The primary and most obvious sign is the complete absence of your period. However, depending on the underlying medical cause, you may experience additional symptoms, including: Milky discharge from the nipples (galactorrhea...