2D:4D ratios as an indicator of intrauterine androgen exposure in children who stutter.

Aim: We aimed to explore whether there is a relationship between stuttering and digit ratio (2D:4D), which is thought to be a marker of prenatal testosterone exposure.

Methods: We evaluated a total of 90 children who stutter (CWS; n = 40 mild-to-moderate and n = 50 severe stutters) and 40 healthy peers (CWNS) as controls. We used the Clinical Global Impression-Severity (CGIS) scale to measure the severity of stuttering. We measured the lengths of index finger (2D) and ring finger (4D) of both hands directly and divided to calculate 2D:4D ratio. The difference between the right and the left hand 2D:4D ratio (D) was also calculated.

Result: Significant difference was found in right 2D:4D and the mean D between the CWS and CWNS groups. Right 2D:4D was significantly lower in stuttering boys than in control boys, and in stuttering girls than control girls. Also, D was significantly lower in stuttering boys than control boys. In ANOVA, there were significant differences between the mild-to-moderate, severe stuttering and control groups in terms of right 2D:4D and D. Right hand 2D:4D and D decreased from controls to severe stutterers.

Conclusion: Our results suggest that lower right 2D:4D and D were related to the presence and severity of stuttering in children, i.e. CWS had lower 2D:4D and D than CWNS. Further large-scale prospective studies are needed to clarify the reliability of 2D:4D ratio as an indicator of fetal sex hormone exposure level and its relation with the presence and severity of stuttering in children.