MONDAY, July 4, 2011 (HealthDay News) -- A look at the relative length of a man's index and ring fingers might be a good predictor of the length of his penis, according to South Korean researchers.
They found that the ratio between the second and fourth digits on a man's right hand seemed to correlate to the length of his flaccid and stretched penis, with a lower index-to-ring finger length ratio indicating a longer penis.
The key to this relationship may lie in the womb, the team added.
"During the fetal period, high concentrations of testosterone lead to high testicular activity, resulting in a lower digit ratio," explained a team led by In Ho Choi of Gacheon University Gil Hospital in Incheon. "In the present study, patients with a lower digit ratio tended to have a longer stretched penile length."
They added that the length of the stretched and flaccid penis does show "a strong correlation" with an erect penile length.
The study was published July 4 in the Asian Journal of Andrology.
The researchers noted that penile length and the second-to-fourth digit ratio in males are "thought to be fixed early in development." In each case, this involves a common set of genes that regulate prenatal hormones (including testosterone) to influence both limb development and the development of the urogenital system.
In the new study, Choi and colleagues compared the digit ratios of 144 Korean men aged 20 and older who were being treated for urological surgery. Researchers measured the index and ring fingers of each man's right hand and compared the ratio to the length of each man's fully stretched, flaccid penis (the latter data obtained under anesthesia).
In a journal commentary, Denise Brooks McQuade of Skidmore College, Saratoga Springs, N.Y., said the study results "provide convincing support for a relationship between digit ratio and penile length." She added that the findings might have real value for research into clinical conditions linked to developmental issues in men.
There's more on male sexual development at 4Parents.gov.