Glossary — O

An oncologist is a physician who focuses on cancer care — from diagnosis through treatment and follow-up. Depending on their specialty, they may use surgery, chemotherapy, radiation, immunotherapy, or targeted therapies to treat tumors in various parts of the body.

An oophorectomy is the surgical removal of one ovary (unilateral) or both ovaries (bilateral). It may be performed to treat ovarian cysts, cancer, endometriosis, or to reduce cancer risk in women with certain genetic mutations, such as BRCA1 or BRCA2.

Osteopenia describes bone mineral density that is below the normal range for a young adult but not low enough to be classified as osteoporosis. It's considered a warning stage — bones are weaker than ideal, but the risk of fracture is lower than with full osteoporosis, and bone loss can often be slowed or reversed.

Osteoporosis is a disease in which bones lose density and structural strength, making them porous and prone to breaking — sometimes from a minor fall or even routine movement. It affects millions of people, most commonly postmenopausal women, and is often called a "silent" disease because it causes no symptoms until a fracture occurs.

Ovarian cancer refers to malignant tumors that originate in the ovaries, the almond-shaped organs that produce eggs and hormones. It is one of the more challenging gynecologic cancers because it frequently causes vague symptoms in early stages, and no reliable screening test yet exists for women at average risk.

Ovulation is the process by which one of the ovaries releases a mature egg, typically once per menstrual cycle. The egg then travels down the fallopian tube, where it may be fertilized. Ovulation is triggered by a surge in luteinizing hormone (LH) and usually occurs around the midpoint of a 28-day cycle.