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Klinefelter’s Syndrome

and Digit Ratio (2D:4D)

 

A classic indicator of KS is low testosterone levels.

A man’s production of testosterone has two peak periods. The first occurs at the end of the first trimester of foetal development in the womb. The second occurs at puberty. It is thought that the prenatal peak is concerned with “organizational” changes to the foetus and may affect the level of testosterone at puberty and in adulthood.

According to research by Prof John T. Manning who has written  “Digit Ratio: A Pointer to Fertility, Behaviour, and Health (A volume in the Rutgers Series in Human Evolution)”, digit ratio (the ratio between the length of the 2nd or index finger and the 4th or ring finger - or 2D:4D for short) is thought to be a marker of foetal levels of testosterone. A long index finger relative to ring finger indicates low foetal testosterone and vice versa. If this is correct it would be expected that KS individuals would have long index fingers relative to their ring fingers.  Professor Manning would like to test this hypothesis with our help.

 

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