Primary amenorrhea is defined as the pathologic absence of menses by age 13 with no secondary sexual characteristics, or by age 15 regardless of secondary sexual characteristic development, and reflects a disruption somewhere along the hypothalamic-pituitary-ovarian (HPO) axis, whose intact function (hypothalamic GnRH release, anterior pituitary FSH/LH secretion, ovarian estrogen/progesterone production, and their withdrawal) is required for a normal menstrual cycle. Causes are differentiated by the presence or absence of breast development and by FSH level (high vs. low), spanning anatomic, gonadal, and central (hypothalamic-pituitary) etiologies within reproductive endocrinology/gynecology.
Primary amenorrhea is the absence of menstruation at a defined age threshold (13 without secondary sexual characteristics, or 15 regardless of their presence), reflecting a disruption anywhere along …