Primary amenorrhea is diagnosed when a woman does not get her period by the age of 14 or 16 years of age. It is diagnosesd when the woman never had a period. Socondary amenorrhea is diagnosed when a woman who previously had a period now does not have one.

Primary amenorrhea is defined as:

• An absence of menses by age 14 years with the absence of growth or development of secondary sexual characteristics (e.g. breast development), OR
• An absence of menses by age 16 years with the normal development of secondary sexual characteristics.

Secondary amenorrhea is defined as:

• The cessation of menstruation for at least 6 months or for at least 3 of the previous 3 cycle intervals (The 2 main reasons for secondary amenorrhea are pregnancy and menopause)

There are several main reasons  for primary amenorrhea:

1. The absence of the uterus and/or the vagina, uterine agenesis, vaginal agenesis (Müllerian agenesis aka Mayer–Rokitansky–Küster–Hauser syndrome)
2. Androgen insensitivity syndrome
3. Turner syndrome (45, XO)

Vaginal Agenesis

This is the congenital absence of a vagina. Women without vagina do not menstruate.

Androgen Insensitivity Syndrome

When the body lacks the ability to respond to male hormones there is the appearance of a female despite having a male chromosomal pattern and gonadal production of male hormones. However, the person does not have a uterus or periods, pubic and axillary hair are scant, and testosterone levels are in the male hormone range.

Turner Syndrome

Turner syndrome is a common genetic condition in which where one of the X chromosomes is missing, and the person has 45 (45, X) instead of 46 chromosomes (46, XY or 46, XX). This is usually associated with absent menses and failure to develop ovaries. Without ovaries, you will develop as a female but never undergo puberty.

Other causes of primary amenorrhea

• Low body weight
• Stress
• Intense exercise (such as experienced by gymnasts or ballet dancers)
• Obesity associated with the polycystic ovarian syndrome may be involved in primary amenorrhea

Testing

When there is primary amenorrhea, the doctor's first step would be to do a pregnancy test, then test blood for the hormone FSH. If this is elevated, a chromosomal evaluation is in order.  A careful physical examination, transvaginal ultrasound, and FSH blood test can help your physician narrow the possibilities.