Men over 30 who contract Covid-19 are more likely to have a severe course than women who are also ill. Their risk of death is also significantly higher. These facts are not new, this has also been observed with Sars-CoV-1 and Mers, two other corona viruses. For Sars-CoV-2, it was already apparent in the first wave of infections in China, Italy and the USA, but also in Germany. Why?