Inhibin-A

Function

Inhibin-A is a peptide hormone produced primarily by the granulosa cells of the ovaries in women and the Sertoli cells of the testes in men. Its primary biological role is the feedback inhibition of Follicle-Stimulating Hormone (FSH) secretion from the anterior pituitary gland. In pregnant women, Inhibin-A is produced by the placenta and levels rise significantly during the second trimester.

Why it is Ordered

This test is most commonly ordered for two reasons: as part of the 'Quad Screen' during prenatal testing and as a tumor marker. In prenatal care, it is used between the 15th and 20th weeks of pregnancy to assess the risk of chromosomal abnormalities. Outside of pregnancy, it is utilized to monitor patients with suspected or previously treated ovarian granulosa cell tumors.

Associated Conditions

• Down Syndrome (Trisomy 21): Elevated Inhibin-A levels in the second trimester are associated with an increased risk of Down Syndrome.
• Ovarian Cancer: Specifically, mucinous and granulosa cell tumors often secrete high levels of Inhibin-A, making it a valuable tool for monitoring recurrence or response to therapy.
• Preeclampsia: Some research suggests that abnormally high levels in early pregnancy may correlate with a higher risk of developing preeclampsia later in the term.

Summary

While not a standalone diagnostic tool for cancer or chromosomal issues, Inhibin-A serves as a critical biomarker that, when combined with other data, provides a clear picture of reproductive health and fetal development.