Detailed definition
The ovaries are paired almond-shaped organs located in the pelvis adjacent to the uterus, suspended by the broad ligament. Each ovary contains a finite cohort of primordial follicles — approximately 1–2 million at birth, declining to roughly 25,000 by age 37 and a few hundred by menopause. Each menstrual cycle, a cohort of follicles is recruited; one becomes dominant, ovulates, and forms the corpus luteum that produces progesterone for the luteal phase. Granulosa cells of growing follicles produce estradiol; theca cells produce androgens that granulosa cells aromatize to estradiol. The ovary also produces inhibin B (suppressing pituitary FSH) and AMH (a marker of follicle pool size). Ovarian aging is characterized by progressive follicle depletion, declining inhibin B and AMH (with rising FSH as a consequence), and eventually cessation of ovulation and estradiol production at menopause.
Why it matters in menopause
Menopause is fundamentally an ovarian event — the rest of the endocrine and physiologic changes follow from the loss of ovarian estrogen and progesterone production. Removing the ovaries surgically (oophorectomy) abruptly produces the same end state as natural menopause, with rapid onset of severe symptoms.