GLOSSARY

Inhibin is a glycoprotein hormone made in the gonads that specifically inhibits FSH release from the anterior pituitary, with little effect on LH. It belongs to the TGF-β family and has two main forms.

Types

• Inhibin A: mainly from the corpus luteum and dominant follicle of the ovary and, in pregnancy, from the placenta.
• Inhibin B: in men from Sertoli cells, and in women from small growing follicles in the early follicular phase.

Activin

Activin is related to inhibin but has the opposite effect, stimulating FSH release. The protein follistatin binds activin and neutralises its effect.

Clinical Importance