Activin B

Where it comes from

Made in

Pituitary gonadotrophs, liver, kidney, skin and the ovary

Sent out by

Inflammation in the liver; the cycle in the pituitary and ovary

Acts on

• Pituitary (FSH)
• Hepatocytes (hepcidin)
• Skin and hair follicle
• Islets

What it does

• The pituitary’s own activin, driving FSH from within the gland
• Raised by inflammation, it drives hepcidin in the liver and so locks iron away, which is part of the anaemia of inflammation ¹
• Mice lacking its chain fail to fuse their eyelids before birth; the males breed normally, and the females’ young do not survive ²

In medicine

• No medicine of its own. The approved activin traps, luspatercept and sotatercept, catch activin B along with activin A
• Not measured in care: the assays are research ones, and few laboratories run them

Beyond the body’s own use

• Studied as a driver of kidney fibrosis: injured tubular cells make it, and it activates the fibroblasts around them in mice ³
• Studied as a marker in early pregnancy loss. In one case-control series the serum level was lower in tubal ectopic pregnancy than in a normal pregnancy, but it could not separate an ectopic from a miscarriage ⁴