Progesterone and bad fathering

The hormone progesterone serves vital functions in women who are becoming mothers. It helps keep pregnancies healthy, and it primes pregnant women to show maternal behavior at birth.

That's been known for a long time. What hasn't been clear is the role of progesterone in men--in particular, how it affects their paternal behavior.

It's considered bad form to knock out progesterone in men to see what happens (or to shoot 'em up with it). But Teresa Horton of Northwestern University has done those experiments with male mice.

She has shown (in a chapter in this recent book) that when the effects of progesterone are blocked in male mice, they become better fathers. Progesterone, in other words, has the opposite effect in men that it has in women: It encourages good mothering, and bad fathering. Male mice whose progesterone is blocked are better fathers and they are less likely to kill their pups.

When males are given progesterone concentrations similar to what females have during pregnancy, they become infanticidal, and it lasts for at least five days after the concentration is reduced.

Researchers have known since the 1930s that progesterone was important in maintaining pregnancy. But it hasn't been studied in fathers until very recently. Why? For my speculation, see my previous posts, Where are the Fathers?