Definition of Inhibin

Inhibin: One of two hormones (designated inhibin-A and inhibin-B) secreted by the gonads (by Sertoli cells in the male and the granulosa cells in the female) and that inhibit the production of follicle-stimulating hormone (FSH) by the pituitary gland. The inhibins are also involved in the control of the production of gametes and embryonic and fetal development. Because inhibin-A is elevated in the blood serum of women carrying a fetus with Down syndrome, inhibin-A is included in the maternal serum screening tests for Down syndrome in the second trimester of pregnancy.