Inhibin A, Tumor Marker, Serum in Thiruvananthapuram

Know More About This Test

Inhibin A is a hormone produced mainly by the ovaries and placenta. It plays a role in regulating follicle-stimulating hormone (FSH). This test is commonly used in prenatal screening and female fertility evaluation. It is also used in monitoring certain ovarian tumors.

Why Is This Test Recommended?

You may need this test to:

• Estimate the risk of Down Syndrome (Trisomy 21) in the fetus during the second trimester - typically between 15 and 20 weeks of gestation where elevated Inhibin A is a key indicator
• Improve the accuracy of prenatal risk assessment for Down syndrome when added as a fourth marker to the triple screen panel of AFP, estriol, and hCG
• Aid in the diagnosis, staging, and monitoring of non-epithelial ovarian tumors particularly Granulosa Cell Tumor and Mucinous Ovarian Carcinomas where elevated Inhibin A levels typically decrease after successful tumor removal
• Assess ovarian reserve and function in women being evaluated for fertility, particularly when ordered alongside Inhibin B and FSH
• Monitor for recurrence of Inhibin A-secreting ovarian tumors following surgical treatment or chemotherapy
• Evaluate unexplained infertility or irregular menstrual cycles where ovarian hormonal function requires assessment

Symptoms or Conditions That May Require an Inhibin A, Serum Test

You may need this test if you:

• Are between 15 and 20 weeks pregnant and are undergoing second-trimester maternal serum screening as part of routine antenatal care
• Have a positive or borderline first-trimester combined screening result (nuchal translucency + PAPP-A + beta-hCG) that requires further second-trimester risk stratification
• Are of advanced maternal age (35 years or older) with an inherently higher risk of fetal chromosomal abnormalities
• Have a personal or family history of chromosomal disorders or a prior pregnancy affected by Down syndrome
• Experience unexplained pelvic pain, abdominal bloating, or irregular periods that require evaluation for an ovarian tumor
• Have been previously diagnosed with a granulosa cell tumor or mucinous ovarian carcinoma and are undergoing post-treatment surveillance
• Are being investigated for premature ovarian insufficiency or difficulties conceiving, where ovarian hormonal profiling is clinically indicated

Advantages of the Inhibin A, Serum Test

The Inhibin A test delivers significant clinical value across two distinct medical domains within a single, non-invasive blood draw. The Quad screen test performance has been validated by several large studies, detecting about 80% of Down syndrome pregnancies at a 5% false-positive rate a detection rate that represents a substantial improvement over earlier screening panels that did not include Inhibin A.

Including the fourth marker, Inhibin A, increases both the sensitivity and specificity of the screen for Down syndrome making the Quad screen the most accurate non-invasive second-trimester chromosomal risk assessment available without resorting to invasive diagnostic testing.

How Is the Test Performed and Prepared For?

Blood sample is collected. No fasting is required. Inform your doctor of pregnancy status.

What Do the Results Mean?

In the prenatal screening context (Quad Screen):

• Second-trimester maternal serum analyte screening results are categorized as low-risk or high-risk based on characteristic analyte patterns associated with specific chromosomal conditions
• Results are expressed as a Multiple of the Median (MoM) — an Inhibin A MoM of approximately 1.0 reflects the median value for a normal pregnancy at the same gestational age; values significantly above 1.0 contribute to an elevated Down syndrome risk score
• The mean Inhibin A multiple of the median is significantly higher in Down syndrome pregnancies compared to chromosomally normal pregnancies typically approximately twice the median value seen in unaffected pregnancies
• Low-risk result: The combined Quad screen risk estimate falls below the established threshold (typically less than 1 in 270 for Down syndrome) - routine antenatal care continues
• High-risk result: The combined risk estimate exceeds the threshold - this is not a diagnosis but an indication that further evaluation through genetic counselling and, if appropriate, diagnostic amniocentesis is recommended. It is important to note that positive screening tests are not diagnostic of a fetal abnormality - while they indicate increased risk, only a small number of women with positive results have babies who actually have a chromosomal abnormality

Lifestyle Tips During Prenatal Screening and Cancer Surveillance

• Attend all scheduled antenatal appointments and blood tests in the recommended gestational windows the clinical value of second-trimester screening is entirely dependent on testing at the correct time
• Engage with pre-test and post-test genetic counselling when undergoing prenatal Quad screening understanding what the results mean, and what they do not mean, is essential for informed decision-making
• Maintain a balanced, nutrient-rich diet during pregnancy, ensuring adequate folic acid, iron, and calcium intake to support fetal development during the critical second-trimester period when this test is performed
• If being monitored for an ovarian tumor, attend all scheduled follow-up appointments and Inhibin A monitoring tests without delay consistent surveillance is the most effective strategy for early detection of recurrence
• Avoid self-medicating with hormonal supplements or fertility drugs during the screening period without medical guidance, as these can directly interfere with Inhibin A levels and compromise the accuracy of prenatal risk calculations
• Report any new gynaecological symptoms including pelvic pain, abdominal bloating, or irregular bleeding to your doctor promptly, particularly if you have a history of an Inhibin A-secreting ovarian tumour

Frequently Asked Questions (FAQs)

1. Is it only for pregnant women? No; Inhibin A testing is also used for fertility evaluation, ovarian function assessment, and monitoring certain ovarian tumors in non-pregnant women.
2. Does high mean cancer? Not always; elevated Inhibin A can occur in normal pregnancy, ovarian cysts, or tumors, requiring further evaluation and correlation with imaging.
3. Is fasting needed? No; this test does not require fasting and can be performed at any time of day.
4. Is it a diagnostic test? No, screening only; Inhibin A is used for risk assessment and requires correlation with other markers and tests for definitive diagnosis.
5. Is it repeated? Yes, for monitoring; repeat testing may be needed during pregnancy follow-up, fertility treatment, or ovarian tumor surveillance to track changes.