Masculinized Finger Length Patterns in Human Males and Females with Congenital Adrenal Hyperplasia

@article{Brown2002MasculinizedFL,
  title={Masculinized Finger Length Patterns in Human Males and Females with Congenital Adrenal Hyperplasia},
  author={Windy M. Brown and Melissa Hines and Briony A. Fane and Stephen M. Breedlove},
  journal={Hormones and Behavior},
  year={2002},
  volume={42},
  pages={380-386}
}
The ratio of the length of the second digit (2D) to the length of the fourth digit (4D) is greater in women than in men. Since androgens are involved in most somatic sex differences and since the sexual dimorphism in 2D:4D is stable from 2 years of age in humans, it was hypothesized that finger length pattern development might be affected by early androgen exposure. Human females with congenital adrenal hyperplasia (CAH) are exposed prenatally to higher than normal levels of adrenal androgens… 
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The 2D:4D ratio, thus, seems to increase after birth in both men and women, with the second digit growing faster than the fourth digit (positive allometric growth of digit two) and perhaps more so in women than in men.
In-utero androgen exposure and 2nd to 4th digit length ratio-comparisons between healthy controls and females with classical congenital adrenal hyperplasia.
TLDR
2D:4D ratios determined directly from radiographs of the left hand confirm significant differences between males and females, however, female patients with virilizing CAH do not have a male digit ratio pattern suggesting that in theleft hand digit ratio development is not influenced by in-utero exposure to androgens.
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Sexual differences in the index to ring finger length ratio (2D:4D ratio) have been observed since more than 150 years ago, and they are already present in the foetus, although differences between sexes are subjected to ethnic variations.
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2:4D and 4D:H may represent powerful tools to investigate the relationships between fetal environment, offspring phenotype and maternal life history at mechanistic and evolutionary levels and suggest that maternal fecundity co-varies with length ratios.
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Sex Differences and Age Changes in Digit Ratios: Implications for the Use of Digit Ratios in Medicine and Biology
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2D:4D, 2D:3D and 3D: 4D are the most likely digit ratios to reflect levels of prenatal sex steroids, and diseases that show a sex difference in their expression may be influenced by PT and PE.
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