Around one in 500 men could be carrying an extra X or Y chromosome, most of them unaware, according to researchers at the universities of Cambridge and Exeter. This puts them at increased risk of diseases such as type 2 diabetes, atherosclerosis and thrombosis, the researchers report in a study published in Genetics in Medicine.
They analysed genetic data collected on over 200,000 men aged 40-70 from UK Biobank, a biomedical and anonymised database on half a million UK participants. They found 356 men who carried either an extra X chromosome or an extra Y chromosome.
Sex chromosomes determine our biological sex. Men typically have one X and one Y chromosome, while women have two Xs. However, some men also have XXY or XYY.
In the study, the researchers identified 213 men with an extra X chromosome and 143 men with an extra Y chromosome. As the participants in UK Biobank tend to be ‘healthier’ than the general population, this suggests that around one in 500 men may carry an extra X or Y chromosome, they said.
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Only a small minority of these men had a diagnosis of sex chromosome abnormality on their medical records or by self-report: 23% men with XXY and only one of the 143 XYY men (0.7%) had a known diagnosis.
By linking genetic data to routine health records, the team found that men with XXY have much higher chances of reproductive problems, including a three-fold higher risk of delayed puberty and a four-fold higher risk of being childless. These men also had significantly lower blood concentrations of testosterone. Men with XYY appeared to have a normal reproductive function.
Men with either XXY or XYY had higher risks of several other health conditions. They were three times more likely to have type 2 diabetes, six times more likely to develop venous thrombosis, three times as likely to experience pulmonary embolism, and four times more likely to suffer from chronic obstructive pulmonary disease (COPD).
Source: Cambridge University