Use of the 2 D:4 D digit ratio as a biological marker of specific language disorders

Introduction: The finding of biological markers of specific language impairment would facilitate their detection and early intervention. In this sense, the 2 D:4 D finger ratio is considered an indirect indicator of prenatal exposure to testosterone. Previous studies have related it to linguistic competence and aggressive behaviour, and could be a candidate for a biological marker of language impairment. The aim was to compare the value of the 2 D:4 D ratio in children with Specific Language Impairment (SLI) with those of children with typical language development, as well as to establish to what extent this biological index correlates with the behaviour (linguistic, cognitive, social, ...)in both groups. Subjects and methods: 2 D:4 D ratio, language, cognition and social behaviour were compared in a group of children with SLI (n = 15), with a group of children without language difficulties(n = 16) of the same age (between 5-8 years), gender (male), and socio-cultural level. Results: Children with SLI showed significantly higher values of 2 D:4 D ratio of the right hand, and a negative correlation between this ratio and their linguistic competence. Although the children with SLI showed impaired adaptive abilities, but not more aggressive behaviour, these measurements did not correlate with the 2 D:4 D index. Nevertheless, social behaviour correlated with language and cognition competence. Conclusions: A higher value of the biological 2 D:4 D ration (lower intrauterine exposure to testosterone) seems to be associated with language difficulties in boys with SLI, but not with their behavioural difficulties. Their behavioural difficulties seem to be a consequence of their linguistic difficulties and their level of cognition. (C) 2018 Published by Elsevier Espana, S.L.U. on behalf of Asociacion Espanola de Pediatria.