Scientists challenge hormonal theory as to why men have to wait for round two


There are many great mysteries of science: How did life begin? Is the universe infinite? Why does the male of our species need a period of rest after ejaculation before the second round?

This third question may not sound as deep as it is secular, but it indeed baffles scientists.

REVERSE countdown the 20 scientific discoveries which made us say “WTF” in 2021. It is the n ° 15. See the full list here.

Here’s the deal – After ejaculation, males enter a “post-refractory period” which may last longer or shorter depending on the person. But the investigation into why this is happening may have been misled by a molecular red herring: prolactin.

Prolactin is a hormone involved in male and female reproduction. It stimulates, for example, the production of milk in pregnant women. This also applies to orgasms, which for some occur in tandem with ejaculation. Scientists know prolactin spikes during ejaculation and orgasm, leading some scientists to believe that this could be the culprit that slows down the male body’s ability to come back to it after nuts.

Discovery – A to study published earlier this year in the journal Communications biology disputes this theory – and points to another culprit. The study shows that changing prolactin levels in two types of mice had no effect on the refractory period.

The result suggests that the apparent role of prolactin may be a case of correlation confused with causation.

“It means it was just a correlation”, Susana Lima, the study’s first author, said Reverse at the time. “Causation has never been tested.”

If it’s not prolactin, what is it?imageBROKER / Lilly / imageBROKER / Getty Images

How they did it – Lima is a researcher at Champalimaud Research Center for the Unknown, a private biomedical research institution. She and her team studied mice with a short refractory period and mice with a seven-day refractory period. The team drew blood from the male mice at four times:

  • Before you meet female mice for the first time
  • After initially mounting their sexual partner
  • After several edits
  • Post-ejaculation

Blood samples revealed that prolactin increased during sexual activity, but prolactin did not affect the refractory period.

In later experiments, the team artificially altered the prolactin in the blood of each male mouse before intercourse. The altered prolactin levels did not alter the sexual behavior of the mice, which may mean that prolactin is not necessarily a hormone that inhibits sex.

Additionally, the authors blocked the release of prolactin after ejaculation. This change also did not shorten the refractory period.

Why is this important – Humans aren’t mice, but while the prolactin theory may still hold true in humans, Lima says prolactin has similar functions in humans and mice, so she expects consistent results. But the results suggest a different and more nuanced theory of male sexual function: There are several systems and hormones in the body that are involved in the refractory period, and individuals may differ depending on their unique circumstances.

The two main systems involved are a central brain mechanism and a peripheral mechanism. The central mechanism deals with behavioral elements, like human sexual desire, while the peripheral mechanism affects physical elements like the penis, glands and other organs of sexual function.

“Most likely, the central systems and the peripheral systems work in coordination, so that a man does not have an erection without desire and desire without being able to be erect,” says Lima.

REVERSE countdown the 20 scientific discoveries that made us say “WTF” in 2021. It’s # 16. Read the original story here.


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