A study has found that an increased risk of motor neurone disease may be indicated by a long ring-finger.
It is believed that the connection comes from the amount of male hormone testosterone that is present in the womb before birth.
Scientists claim that adult motor nerves are less sensitive to the hormone if there have been high levels of prenatal exposure.
The lengths of the ring and index finger, known as 2D:4D ratio, are believed to be affected by hormones in the womb.
If the ring finger is relatively longer than the index finger it means there is a low ratio, which is more commonly the case among men.
The study has suggested that the most common form of motor neurone disease, amyotrophic lateral sclerosis (ALS), is also linked with a low 2D:4D ratio.
The normally fatal disease causes progressive degeneration of the motor nerves that control movement, as well as weakness and muscle wasting.
Leading physicist Professor Stephen Hawking is one of the best known sufferers of the condition.
Researchers writing in the Journal of Neurology, Neurosurgery and Psychiatry compared 47 ALS patients and 63 healthy individuals.
Although no overall difference in 2D:4D ratio was seen between men and women, it was consistently lower for people with ALS.
The scientists, led by Professor Ammar Al-Chalabi from King’s College London, wrote: “This finger length ratio is thought to be a marker of high prenatal testosterone levels, and our results are therefore consistent with the hypothesis that testosterone levels during development modify the subsequent risk of ALS.”