The ratio of the second and fourth finger lengths (2D/4D ratio) may predict which men have testosterone deficiency, researchers reported.

A prospective study of 204 men referred for prostate biopsy (mean age 67 years) showed that a low 2D/4D ratio is associated with higher levels of testosterone and with a low prevalence of biochemical hypogonadism (defined as a testosterone level below 346 ng/dL).

The mean 2D/4D ratio in men with testosterone levels above 346 was lower than in men with testosterone levels below 346 (0.97 vs. 0.99), the researchers reported online in BJU International.

For the study, investigators at Hospital Clinic de Barcelona in Spain led by Eduardo Garcia-Cruz, MD, determined 2D/4D ratios using a vernier caliper on subjects’ left hand.