Ovaries: Anatomy, Function, and Hormone Production

The ovaries are paired, almond-shaped organs located in the pelvis, one on each side of the uterus. They have two primary functions: gametogenesis and endocrine secretion.

1. Gametogenesis: Egg Production

• Each menstrual cycle, a cohort of follicles begins developing under FSH stimulation.
• Typically, one dominant follicle matures and ovulates (releases an oocyte).
• The oocyte is captured by the fimbriated end of the fallopian tube.

2. Endocrine Function: Hormone Production

• Estrogen (mainly estradiol): Follicular phase; proliferates endometrium, regulates cycle, supports bone, cardiovascular, cognitive health.
• Progesterone: Luteal phase (from corpus luteum); prepares endometrium for implantation, maintains early pregnancy.
• Inhibin, activin, AMH: Regulate FSH, reflect ovarian reserve.
• Androgens (testosterone, androstenedione): Precursors for estrogen; contribute to libido.

The Ovarian Cycle

Each cycle, a cohort of follicles develops; typically one ovulates. The corpus luteum then produces progesterone to prepare the endometrium. If no pregnancy, the corpus luteum regresses → progesterone drops → menstruation begins.

Clinical Relevance

• PCOS: multiple small follicles, anovulation, hyperandrogenism.
• Premature ovarian insufficiency: loss of function before age 40.
• Ovarian cysts: functional (follicular, corpus luteum) vs. neoplastic.
• Ovarian cancer: often silent until advanced; no effective screening for average risk.