Which hormone is known as maternity hormone

Casanova or life sentence?

For a long time it was actually considered the maternity hormone par excellence - oxytocin. It ensures that labor begins during childbirth and stimulates the flow of milk to the mother while breastfeeding. Pregnant women have been receiving artificial oxytocin for years as a labor stimulant if the birth is too long in coming. But the hormone also has dramatic effects on behavior: if it is missing, animal mothers reject their newborns and show no motivation to feed or suckle. Such a connection is now also being discussed for humans.

In recent years, however, researchers have discovered an entirely different aspect of the tiny peptide molecule. This finding was helped by two species of mice native to the western United States, which are closely related to one another, but differ in one decisive characteristic: their social behavior.

A handful of genes and many receptors ...

The prairie vole is extremely monogamous. If a male and a female find each other, this bond is for life. Both then spend most of their time together, prove to be self-sacrificing mothers and fathers and lead an exemplary "marriage" in general. The mountain voles, on the other hand, do not take it that seriously, with them the "one-night-stand" is the rule and otherwise there is also a lack of commitment.

The cause of these differences lies in only a handful of genes - including those responsible for the release and absorption of the hormones oxytocin and vasopressin. As Thomas Insel, a neurologist at Emory University in New York found out, the loyal prairie voles not only have significantly higher levels of oxytocin in their blood, but their brains also have considerably more receptors for this hormone.

... make Casanova a loyal husband

And there was also a connection to social behavior: “If we block oxytocin production, they no longer form long-term relationships. Usually the prairie voles form a permanent bond with the partner with whom they copulate for several hours. Mountain voles do the latter as well, but it does not result in pair bonding, ”explains Insel.

A pair bond, however, presupposes that the vole can remember with whom it has just copulated extensively. Research by neurologist Young shows that this is actually the case with the prairie vole in the form of a “smell” of its partner - but only when the hormones oxytocin and vasopressin are present. Voles with inactivated oxytocin or vasopressin genes promptly suffered from social amnesia and no longer recognized conspecifics at all.

A similar principle could possibly apply not only to voles but also to other mammals - including humans. The American neuroscientist Diane Witt has examined, among other things, the mother-child relationship in rats and other mammals and here again determined decisive hormonal influences that she considers to be transferable to humans. “A pathological situation in which there is too much oxytocion or an increased sensitivity to the hormone could lead to excessive attachment or even pedophilia. Too little, on the other hand, is a contributory cause of pathological indifference and neglect towards the child.

Status: November 19, 2004

November 19, 2004