Placental growth hormone

Where it comes from

Made in

Syncytiotrophoblast of the placenta

Sent out by

Continuously, not in pulses; between about 12 and 20 weeks it takes over the mother’s blood from her pituitary, and glucose alters its output

Acts on

• Maternal liver (IGF-1)
• Maternal fat and muscle (insulin resistance)
• Placenta itself

What it does

• Replaces the mother’s pituitary growth hormone, which is switched off ¹
• Raises maternal IGF-1 and makes her tissues insulin-resistant so glucose goes to the fetus ¹
• Tracks fetal growth: a low maternal level goes with a smaller baby ²

In medicine

• A research marker of placental function and fetal growth. It is not measured in routine care and no assay for it is standardised
• Reported raised in severe pre-eclampsia, in the mother’s blood and in cord blood, but not raised when pre-eclampsia came with growth restriction, so it is not a usable test ³

Beyond the body’s own use

• Nobody is given it. Pituitary growth hormone is the medicine; this variant has never been made as a drug, and no trial has tested it
• It is studied as a window on the placenta: because it comes from syncytiotrophoblast and nowhere else, its level in maternal blood is close to a direct count of placental output ¹