Elevated Inhibin B and Ovarian Cancer
An elevated inhibin B level alone is not a reliable indicator of ovarian cancer. While inhibin B can be dramatically increased in certain ovarian tumors, particularly granulosa cell tumors, it lacks specificity as a tumor marker for ovarian cancer, even at very high levels 1.
Relationship Between Inhibin B and Ovarian Tumors
- Inhibin B is the major molecular form of inhibin produced by granulosa cell tumors, with levels correlating with clinical disease status 2
- Elevated inhibin B has been documented in benign ovarian conditions, including thecomas, which can mimic granulosa cell tumors with markedly elevated inhibin B levels 1
- While inhibin levels (particularly inhibin B) are frequently elevated in granulosa cell tumors, they can also be elevated in mucinous cystadenocarcinomas and less frequently in other forms of ovarian tumors 3
Diagnostic Value of Inhibin B
- Serum inhibin B was found to be dramatically increased in 8 of 9 patients with granulosa cell tumors in one study, but was not elevated in patients with epithelial ovarian cancers 2
- Multiple forms of inhibin proteins can be present in serum from postmenopausal women with epithelial ovarian cancer, with pro-alphaC inhibin showing more promise as a potential marker than inhibin B 4
- In postmenopausal women, elevated inhibin concentrations were found in 82% of women with mucinous carcinomas but only in 17% of women with serous carcinomas 5
Tumor Markers in Ovarian Cancer Diagnosis
- CA-125 remains the standard tumor marker for epithelial ovarian cancer, elevated in approximately 85% of patients with advanced disease but only about 50% of early-stage cases 6
- For definitive diagnosis of ovarian cancer, pathological examination of tumor samples from either a diagnostic biopsy or surgical specimen is required 7
- When evaluating potential ovarian cancer, measurement of serum CA-125 aids diagnosis but is not specific to ovarian cancer and may be elevated in non-gynecological malignancies and benign conditions 7
Clinical Approach to Elevated Inhibin B
- If ovarian cancer is suspected, a comprehensive diagnostic workup should include:
- Detailed history and clinical examination
- Serum CA-125 measurement
- Transabdominal and transvaginal ultrasound by an expert examiner
- CT of thorax, abdomen and pelvis 7
- For mucinous tumors, measuring serum CEA and CA 19-9 in addition to CA-125 may help distinguish primary ovarian tumors from gastrointestinal metastases 7
- Inhibin B should be interpreted alongside other clinical findings and imaging results, as it can be elevated in benign conditions 1
Important Caveats
- An elevated inhibin B level should prompt further evaluation but is not diagnostic of ovarian cancer on its own 3
- Knowledge of benign alternative explanations for elevated inhibin B can facilitate improved preoperative patient counseling 1
- Inhibin levels typically fall after tumor removal, which can be useful for monitoring purposes 5