Thread by @yffei

Ready for another #PAG mystery?
16yo with primary amenorrhea (never started periods).
What questions do you want to ask?
#MedTwitter #MedEd #tweetorial #OBGYNtwitter

There are many reasons someone might not have periods. I usually divide them into sections to make them easier to rule out:
- hormonal: either repro hormones not cycling normally and/or abnormal levels of other hormones
- structural: could be a blockage or underdeveloped organs

Things to think about:
- any evidence of puberty (breasts, pubic/axillary hair, growth spurt)?
- could she be pregnant?
- any other symptoms (acne, facial hair, breast discharge, hot flashes, night sweats)?
- any (cyclic/monthly) abdominal pain?
- exercise and eating habits?

She says breast growth at age 10, pubic hair at age 11. Close to average height for other adult females in the family. Never been sexually active. No abdominal pain. Minimal acne, no facial hair, no other symptoms.

Important things to note on exam:
- facial hair, excess body hair
- breast development
- abdominal mass
- other evidence of virilization
- vaginal length, vaginal mass
- abdominal mass on rectal exam

We know she has at least started puberty and we usually expect periods about 2-3 years after breasts start. This means that her body IS making estrogen. No other major symptoms means that her hormone levels are most likely fine. No abdominal pain means probably no obstruction.

Ultrasound (and confirmatory MRI) show absent uterus. This narrows the differential to mayer-rokitansky-küster-hauser syndrome (#MRKH) or complete androgen insensitivity syndrome (#CAIS). How do you differentiate between two?

In MRKH, the mullerian structures (ie uterus and most of vagina) are underdeveloped. Chromosomes are 46XX and ovaries are functioning normally to produce estrogen.

In CAIS, chromosomes are 46XY. The gonads prevent uterus formation and also make testosterone. However, the body doesn't respond to testosterone so this gets converted to estrogen, leading to typical female puberty.

In both cases, most people are females. Male gender identity is overall rare, likely the same rate as being transgender in the general population.