The Second to Fourth Digit Ratio in Acne Vulgaris

Androgen hormones are thought to play a leading role in acne vulgaris (AV). The 2D:4D digit ratio refers to the ratio of the length of the second finger (index finger) to that of the fourth finger (ring finger). It is thought that the balance between fetal testosterone and fetal estrogen during the prenatal period largely determines this ratio, which does not change with age in the postnatal period.

Patients with no other disease except AV and a control group of healthy patients were included in the study. Sex, age, family history, age of onset, and duration of disease in patients diagnosed with AV were recorded. The lengths of the patients' second and fourth fingers were measured using a digital caliper with a resolution of 0.01 mm. Hormone levels were also measured.

When the 2D:4D ratio for the right hand and the left hand (separately) as well as the average (mean) 2D:4D ratio of both hands in male and female patients were compared with those of the control group, no statistically significant difference was observed. The right 2D:4D ratio of female patients was positively correlated with free androgen index percentage and prolactin values and negatively correlated with sex hormone-binding globulin. The left 2D:4D ratio of female patients was found to be positively correlated with disease duration and follicle-stimulating hormone values.

The 2D:4D ratio was not significantly different between the group with AV and the control group independent of sex. Also, we did not observe a significant association with age of onset, severity of disease, or family history.