More Women Than Expected Are Genetically Men

Summary

BY MORTEN BUSCH Sex chromosomes usually determine whether you are female or male. Women are XX. Men are XY. However, genetically, a few women are actually men. They grow up as women with a woman’s body, and most only discover well into puberty that they are different. Danish researchers map for the first time how many women are genetically men. The proportion was higher than expected. You cannot see it if you do not know what you are looking for. One in 15,000 males is born and grows up as a girl. And neither these girls nor their parents know it. These girls do not discover anything different until puberty. “Girls born with XY chromosomes are genetically boys but for a variety of reasons – mutations in genes that determine sexual development – the male characteristics are never expressed. They live their lives as girls and then women, and a few can even give birth. Our research, which is the first nationwide survey in the world, shows that this group is up to 50% larger than previously assumed. How these girls discover the facts and talk openly about their situation also varies greatly,” explains Claus Højbjerg Gravholt, who led the study and is Clinical Professor in the Department of Clinical Medicine of Aarhus University. Together with colleagues, he is investigating why sex chromosome abnormalities occur and therefore how people with XY chromosomes can become women. Two types of genetic mutations mostly make the difference; these were previously referred to as Morris syndrome and Swyer syndrome but are now collectively referred to as disorders of sex development (DSD). “Morris syndrome is now called 46,XY DSD: androgen insensitivity syndrome. These people have an extremely high level of testosterone and other male sex hormones, but the testosterone does not affect the foetal cells that usually develop into male sexual organs because of a mutation in the androgen receptor gene. These people therefore have male chromosomes but are women socially and in external ap...