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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References

SHOWING 1-10 OF 47 REFERENCES
Sexual dimorphism in digit‐length ratios of laboratory mice
TLDR
The mouse may be a useful animal model for studying the factors that influence finger length patterns, which have recently been correlated with several specific behaviors and disease predispositions in humans.
The ratio of 2nd to 4th digit length: a predictor of sperm numbers and concentrations of testosterone, luteinizing hormone and oestrogen.
TLDR
It is shown that 2D:4D in right and left hands has a sexually dimorphic pattern and is probably established in utero, which raises the possibility that patterns of digit formation may relate to spermatogenesis and hormonal concentrations.
Finger-length ratios and sexual orientation
TLDR
The androgen-sensitive pattern of finger lengths is examined, and there is evidence that homosexual women are exposed to more prenatal androgen than heterosexual women are, and men with more than one older brother, who are more likely than first-born males to be homosexual in adulthood, are exposure to more pregnancies than eldest sons.
Androgen and the development of human sex-typical behavior: rough-and-tumble play and sex of preferred playmates in children with congenital adrenal hyperplasia (CAH).
TLDR
Girls with congenital adrenal hyperplasia, who experience higher than normal levels of androgens prenatally, would show masculinization of behaviors that show sex differences, and the preferences of girls with CAH were masculinized compared to those of unaffected girls.
Finger-length as an index of assertiveness in women
Studies on human sexual development. II. Fetal and maternal serum gonadotropin and sex steroid concentrations.
TLDR
Both fetal and maternal “hCG-LH” levels declined with fetal age, with no apparent sex difference, and overall mean E2 levels in the females were higher than in the males.
Testosterone formation and metabolism during male sexual differentiation in the human embryo.
TLDR
It was concluded that testosterone is the principal androgen formed by the fetal testis at the time of male sexual differentiation.
Genetically Triggered Sexual Differentiation of Brain and Behavior
TLDR
It is argued that "direct genetic" control of sexual differentiation may be as likely to evolve as hormonal control and that neural and nonneural dimorphisms have already been described that are not well explained by classical theories of steroid-dependent sexual differentiation.
Early Androgens Are Related to Childhood Sex-Typed Toy Preferences
TLDR
Girls with congenital adrenal hyperplasia who were exposed to high levels of androgen in the prenatal and early postnatal periods showed increased play with boys” toys and reduced play with girls' toys compared with their unexposed female relatives at ages 3 to 8, suggesting that early hormone exposure in females has a masculinizing effect on sex-typed toy preferences.
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