Many individuals become concerned if they notice their ovaries are different sizes. While this can cause worry, variations in ovarian size are common and often represent normal physiological processes. The human body is rarely perfectly symmetrical, and this applies to internal organs. Understanding what constitutes a normal difference can alleviate anxiety.
Normal Physiological Differences
The human body is not perfectly symmetrical, and this natural variation extends to paired organs like the ovaries. It is common for one ovary to be slightly larger or smaller than the other without any underlying medical reason. This slight anatomical difference is often within the range of normal variation.
An adult ovary during reproductive years typically measures approximately 3 to 5 centimeters in length, 1 to 3 centimeters in width, and 0.5 to 1.5 centimeters in thickness. Its volume usually ranges from 3 to 10 cubic centimeters. A small difference, such as one ovary being up to 1 or 2 centimeters larger than the other, is considered within a normal range and does not affect ovarian function or fertility.
Hormonal and Age-Related Influences
Ovary size can fluctuate significantly due to dynamic hormonal changes throughout a woman’s life and menstrual cycle. These changes are common reasons for temporary or expected size differences.
During the menstrual cycle, one ovary prepares and releases an egg, which can temporarily alter its size. A dominant follicle, containing the developing egg, can grow to about 22 to 24 millimeters (2.2 to 2.4 centimeters) before ovulation. After the egg is released, the remaining follicle transforms into a corpus luteum, a structure that also contributes to the ovary’s temporary enlargement. The ovary involved in this process may appear larger than the other for a portion of the cycle.
Ovarian size also changes considerably with age. From infancy, ovaries progressively increase in size, reaching their peak volume around 20 years of age, with an average volume of about 7.7 milliliters. After the age of 30, ovarian volume gradually declines with each decade. Following menopause, when egg production ceases, ovaries shrink significantly, becoming as small as 2 centimeters with volumes typically less than 2 to 3 milliliters. One ovary may naturally shrink faster or be smaller than the other during this transition.
Underlying Medical Causes
While many ovarian size differences are normal, some medical conditions can cause more significant or persistent discrepancies. These conditions can lead to an ovary becoming noticeably enlarged.
Ovarian cysts are a common cause of ovarian enlargement. Functional cysts, such as follicular cysts or corpus luteum cysts, develop as part of the normal menstrual cycle and usually resolve on their own within a few weeks or months. These can range from 2.5 to 5 centimeters, though some may grow larger, up to 10 centimeters. Other types of cysts, like dermoid cysts, endometriomas (often called “chocolate cysts”), and cystadenomas, do not always resolve on their own and can grow to considerable sizes, with some cystadenomas reaching up to 30 centimeters.
Polycystic Ovary Syndrome (PCOS) is a hormonal imbalance that can affect ovarian size. Women with PCOS often have ovaries that appear enlarged with multiple small follicles, typically measuring up to 8 millimeters. While PCOS can lead to increased ovarian volume, it does not always cause asymmetrical enlargement, and the diagnosis depends on other clinical and hormonal factors. Endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, can also cause ovarian enlargement if it forms endometriomas on or within an ovary. These endometriomas can be 5 to 6 centimeters in size.
Growths such as benign or malignant tumors can cause significant size differences. Benign ovarian tumors, including fibromas or cystadenomas, typically grow slowly and can vary in size, with fibromas often being larger than 3 centimeters and cystadenomas potentially becoming very large. Malignant tumors are rarer but can also lead to substantial ovarian enlargement and may have irregular shapes. Conditions like pelvic inflammatory disease (PID) can also cause swelling and tenderness in one or both ovaries due to infection and inflammation.
When to Seek Medical Consultation
While many variations in ovarian size are normal, certain symptoms warrant a medical consultation. Seeking professional advice ensures an accurate diagnosis and appropriate management.
It is advisable to consult a healthcare professional if you experience persistent pelvic pain, which can manifest as a dull ache or sharp, sudden discomfort. Other concerning symptoms include persistent abdominal bloating or a feeling of fullness, changes in your menstrual cycle such as irregular, heavier, or lighter periods, or pain during sexual intercourse. Changes in bowel or bladder habits, like frequent urination or difficulty emptying your bowels, or unexplained weight changes, nausea, vomiting, or fever, should also prompt a medical evaluation.
A healthcare provider will typically begin with a physical examination and may recommend imaging tests like an ultrasound to assess ovarian size and structure. Blood tests may also be part of the evaluation to check hormone levels or tumor markers, though the latter are not always definitive for benign conditions. Many causes of ovarian size differences are benign, but early diagnosis is important for peace of mind and effective management if a medical condition is present.