It is common for one ovary to appear larger than the other. While variations in ovarian size are often normal, a notable disparity can sometimes indicate an underlying medical condition. Understanding these differences and recognizing when medical attention is warranted can provide clarity and peace of mind.
Understanding Ovarian Size
Ovaries are integral to the female reproductive system, producing eggs and hormones like estrogen and progesterone. These almond-shaped glands, located on either side of the uterus, undergo continuous changes. In reproductive-aged individuals, an average ovary typically measures 2.5 to 5 centimeters in length, 1.5 to 3 centimeters in width, and 0.6 to 1.5 centimeters in thickness, with a volume ranging from 3 to 10 cubic centimeters. Ovarian size naturally fluctuates throughout the menstrual cycle due to follicle development and ovulation. After menopause, hormonal activity decreases, and ovaries typically shrink to 2 to 3 cubic centimeters in volume.
Common Reasons for Size Differences
One frequent reason for temporary size differences relates to the normal menstrual cycle. Each month, several follicles, small fluid-filled sacs containing an immature egg, begin to develop in the ovaries. One follicle typically becomes dominant, growing larger (18 to 25 millimeters) before releasing an egg during ovulation. This dominant follicle can make one ovary appear larger.
After egg release, the ruptured follicle transforms into a structure called the corpus luteum, which produces progesterone. The corpus luteum can be quite large (under 2 to 5 centimeters), temporarily enlarging that ovary. If pregnancy does not occur, it typically breaks down after about 10 days, and the ovary returns to its usual size.
Functional cysts, the most common type of ovarian cyst, also arise from normal menstrual cycle processes. A follicular cyst forms if a dominant follicle fails to rupture and continues to grow and fill with fluid. A corpus luteum cyst develops if the egg release opening seals, accumulating fluid. These functional cysts are harmless, often asymptomatic, and typically resolve within a few menstrual cycles.
Medical Conditions Affecting Ovarian Size
Beyond the normal fluctuations of the menstrual cycle, certain medical conditions can lead to persistent or significant enlargement of one or both ovaries. Polycystic Ovary Syndrome (PCOS) is a common condition with hormonal imbalances, irregular periods, and multiple small follicles. Many individuals with PCOS have enlarged ovaries (volume greater than 10 cubic cm) containing numerous small follicles (2 to 9 mm). These follicles do not develop or release eggs properly, contributing to irregular ovulation.
Endometriosis occurs when tissue similar to the uterine lining grows outside the uterus, sometimes forming endometriomas, or “chocolate cysts,” on the ovaries. These cysts vary in size, contributing to ovarian enlargement, and often appear bilateral.
Benign ovarian tumors can also enlarge an ovary. Dermoid cysts (mature cystic teratomas) are a type of benign tumor that can contain various tissues like hair, skin, or teeth, as they form from reproductive cells. These cysts are typically slow-growing, but their size can range from very small to quite large, with some reaching up to 45 centimeters in diameter. Cystadenomas, another benign tumor type, develop from cells on the surface of the ovary and can be filled with watery or mucous material, growing up to 30 centimeters. Ovarian fibromas are solid, benign connective tissue tumors, usually less than 7 centimeters in diameter, and are more common in postmenopausal women.
When to Consult a Doctor
While slight variations in ovarian size are common and often normal, certain symptoms warrant a medical consultation. It is important to seek professional medical advice if you experience persistent pelvic pain or discomfort, especially if it is sharp or severe. Other concerning symptoms include persistent bloating, a feeling of fullness or pressure in the abdomen, or changes in bowel or bladder habits, such as needing to urinate more frequently. Changes in menstrual patterns, such as unusually heavy or irregular periods, or unexplained weight changes, should also prompt a visit to a healthcare provider. These symptoms, while potentially indicative of various conditions, could sometimes signal an underlying ovarian issue that requires evaluation. A doctor can perform a physical exam and may recommend imaging tests, such as an ultrasound, to assess ovarian health and determine the cause of any size discrepancies. Early evaluation helps ensure an accurate diagnosis and appropriate management plan if needed.