No Evidence That 2D:4D Is Related to the Number of CAG Repeats in the Androgen Receptor Gene

The document summarizes a meta-analysis from 2013 that examined the potential link between the second-to-fourth digit ratio (2D:4D), a marker of prenatal testosterone effects, and the number of CAG repeats in the androgen receptor gene, which influences testosterone sensitivity. The analysis, which included 14 samples with a total of 1,904 subjects (792 females and 1,131 males), found no significant correlation between the two measures. The study also reviewed conditions related to testosterone, such as androgenetic alopecia and male infertility, and found no strong evidence of a link with CAG repeat number. The conclusion is that normal variability in CAG repeats has little to no effect on testosterone-dependent gene activation and phenotypic traits, and therefore, the 2D:4D ratio remains a valid marker for prenatal testosterone exposure. The study was published without any conflicts of interest and appeared in the journal Frontiers in Endocrinology.