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 also figure in the control of gametogenesis, and embryonic and fetal development. Inhibin-A is elevated in the blood serum of women carrying fetuses with Down syndrome. This discovery led to the inclusion of inhibin-A in the maternal serum screening tests for Down syndrome in the second trimester of pregnancy.