Peptide directoryReproductive

INSL4

A placental peptide of the primates with no receptor found.

Where it comes from

Made in
Syncytiotrophoblast of the placenta, highest in the first trimester
Sent out by
Into maternal blood, early in pregnancy
Acts on
  • Unknown

What it does

  • Cloned from first-trimester placenta as early placenta insulin-like peptide, and found in quantity nowhere else 1
  • Its placenta-only expression is driven by an endogenous retrovirus element that landed in the promoter 2
  • Arose in the primates. No receptor, and no function, has been shown for it

In medicine

  • None. It is not measured in care, and the assays that exist are research ones raised against the precursor
  • Reported as overexpressed and secreted by HER2-positive breast cancer cells with high invasive potential, which is the only disease link so far 3

Beyond the body’s own use

  • What is actually being asked is whether it is a hormone at all: a primate-specific gene, strongly transcribed in the placenta, with no partner protein found in thirty years of looking
  • It is more use as a marker than as a target. Its transcript is one of a handful specific enough to the placenta to pick fetal material out of a mother’s blood 4

Sources

  1. Chassin et al., Cloning of a new member of the insulin gene superfamily (INSL4) expressed in human placenta, Genomics 1995
  2. Bièche et al., Placenta-specific INSL4 expression is mediated by a human endogenous retrovirus element, Biology of Reproduction 2003
  3. Brandt et al., Pro-EPIL is overexpressed and secreted by c-erbB-2-positive cells with high invasion potential, Cancer Research 2002
  4. Boye et al., Novel feto-specific mRNA species for identification of fetal cells from the maternal circulation, Prenatal Diagnosis 2001

This card describes what a medicine is for and what the evidence says; it recommends nothing. Talk to your clinician about anything you read here.