Primary Amenorrhea
Primary amenorrhea is defined as the absence of menses by age 13 years with the absence of secondary sexual characteristics, OR absence of menses by age 15 years in the presence of normal secondary sexual characteristics.
Diagnostic Algorithm (Anatomic vs. Hormonal)
| Phenotype | Key Differential Diagnoses |
|---|---|
| Uterus Absent | Müllerian Agenesis (Mayer-Rokitansky-Küster-Hauser syndrome); Androgen Insensitivity Syndrome (46,XY). |
| Uterus Present + No Secondary Sexual Characteristics | Hypergonadotropic hypogonadism (e.g., Turner syndrome, 46, XX gonadal dysgenesis). |
| Uterus Present + Normal Secondary Sexual Characteristics | Anatomic obstruction (imperforate hymen, transverse vaginal septum); hypothalamic/pituitary dysfunction. |
High-Yield Exam Pearl:
- Androgen Insensitivity Syndrome (AIS): Patients present with primary amenorrhea, absent uterus/ovaries, 46, XY karyotype, and normal breast development (due to peripheral conversion of androgens to estrogens).
- Müllerian Agenesis: Normal secondary sexual characteristics and normal ovarian function, but with an absent or rudimentary uterus/vagina. Karyotype is 46,XX.