Inhibin A is a hormone naturally present in the body, primarily involved in reproductive processes. It has also been identified as a biological indicator for certain types of ovarian cancer. Its levels can provide valuable information for understanding and managing these specific malignancies, offering insights into its connection with particular tumor types and its utility in clinical settings.
The Biological Role of Inhibin A
Inhibin A is a protein hormone predominantly produced by granulosa cells within ovarian follicles. Its primary role involves a negative feedback loop that regulates the menstrual cycle. This hormone acts on the pituitary gland, a small gland located at the base of the brain.
Inhibin A’s main function is to suppress the secretion of follicle-stimulating hormone (FSH) from the pituitary gland. During the luteal phase, the corpus luteum becomes a significant producer of inhibin A, alongside progesterone and estradiol. This combined hormonal signal helps lower FSH levels, preventing the development of new follicles.
Connection to Ovarian Cancer Subtypes
While inhibin A plays a normal role in reproductive regulation, its production can become dysregulated in certain ovarian tumors. High levels of inhibin A are associated with specific ovarian cancer subtypes. Granulosa cell tumors frequently secrete elevated inhibin A levels, found in approximately 70% of patients.
These tumor cells often mimic normal granulosa cells, leading to inhibin A overproduction, making it a useful marker for these malignancies. Elevated inhibin A levels may also be present in some women with mucinous epithelial ovarian cancers, with about 20% of cases showing elevated levels.
Inhibin A is not a universal marker for all ovarian cancers. It is not a strong marker for common epithelial ovarian cancer subtypes like serous or endometrioid carcinomas. Therefore, while its elevation suggests granulosa cell tumors or, less commonly, mucinous tumors, normal inhibin A levels do not exclude other forms of ovarian cancer.
Clinical Use as a Biomarker
Measuring inhibin A levels in the blood offers a practical application in the initial evaluation of suspected ovarian tumors. The test involves a simple blood draw. Elevated inhibin A levels, when considered alongside other clinical findings like a pelvic mass, can suggest specific ovarian tumor types such as granulosa cell tumors or mucinous epithelial ovarian tumors.
Inhibin A testing is not a standalone diagnostic tool. Its results are interpreted with other diagnostic methods for a comprehensive picture. These often include imaging techniques like ultrasound or CT scans, and other established tumor markers such as CA-125. While CA-125 is common for epithelial ovarian cancers, inhibin A is valuable for types where CA-125 may be less effective, like granulosa cell and mucinous tumors.
For premenopausal women, interpreting inhibin A levels can be complex due to natural menstrual cycle fluctuations. Postmenopausal women typically have very low or undetectable inhibin A levels, making any elevation more indicative of a tumor. A pathologist will examine tissue samples to confirm cancerous cells, as elevated inhibin A levels alone do not definitively diagnose cancer.
Monitoring Treatment and Detecting Recurrence
Inhibin A also serves a valuable role after an ovarian cancer diagnosis, particularly for monitoring treatment effectiveness and detecting potential recurrence. If a patient’s tumor initially produced high inhibin A levels, successful treatment, such as surgery or chemotherapy, should significantly decrease these hormone levels. This reduction indicates the tumor mass has been reduced or removed and is responding to therapy.
Doctors can track inhibin A levels over time through regular blood tests following treatment completion. A subsequent rise in these levels after normalization can indicate the cancer has returned, sometimes before it is detectable through imaging or symptoms. This allows for earlier intervention, potentially improving outcomes and providing an objective measure of disease status.