Digit ratio (2D:4D) in Klinefelter's syndrome

Abstract

SUMMARYThe ratio of second to fourth digit length (2D:4D) is a correlate of prenatal testosterone. High 2D:4D is associated with low prenatal testosterone, and reduced sensitivity to testosterone. Klinefelter's syndrome (KS; 47 XXY) affects the endocrine system, such that low testosterone levels are found in KS foetuses, new-borns and adults. To date, there are no published data regarding the pattern of 2D:4D in KS males. Here we consider 2D:4D in KS individuals (n = 51), their relatives (16 fathers and 15 mothers) and an unaffected control sample of 153 men and 153 women. Adult KS individuals were taller than their fathers and had shorter fingers than fathers and male controls. Compared with fathers, male controls and mothers, KS males had shorter fingers relative to height. With regard to 2D:4D, KS individuals had higher 2D:4D than fathers (right and left hands), male controls (right and left hands) and mothers (left hands). Among KS males older than 13 years there were 34 individuals currently prescribed testosterone and nine not prescribed. In comparison to the former, the latter individuals had higher right 2D:4D and higher right-left 2D:4D. We conclude that KS males have mean 2D:4D values similar to those found in female population norms. In addition, testosterone supplementation in KS males may be most common for individuals with low right 2D:4D.

Visuo-Spatial Performance in Autism: A Meta-analysis

“…Further, digit ratio 2D:4D (i.e. index finger length divided by ring finger length) is believed to be a marker of prenatal testosterone exposure (Manning et al 2013) and it is more male-typical in individuals with ASD than in TD individuals (Hönekopp 2012). Baron-Cohen (1999) lists evidence from research on tasks on which females are generally superior to males, and indeed these tasks are impaired in autism.…”

Differences in salivary testosterone, digit ratio and empathy between intellectually gifted and control boys

“…According to many studies, 2D:4D ratio reliably reflects prenatal hormonal levels. Low 2D:4D ratio points to a high exposure to testosterone in the uterus (Manning, Kilduff, & Trivers, 2013;Manning & Robinson, 2003;Neave, Laing, Fink, & Manning, 2003;Paul, Kato, Hunkin, Vivekanandan, & Spector, 2006). This parameter is believed to be fixed in utero.…”

Digit ratio, emotional intelligence and parenting styles predict female aggression

“…Critical for this research is that the ratio of the second (index) finger length to fourth (ring) finger length (2D:4D) is a marker of prenatal T, with smaller ratios indicating greater exposure. For example, males with Klinefelter's syndrome (KS; an endocrine disorder marked by low T levels beginning prenatally) have higher (feminized) 2D:4D compared to fathers, male controls, and mothers (Manning, Kilduff, & Trivers, 2013). Lutchmaya, Baron-Cohen, Raggatt, Knickmeyer, and Manning (2004) measured T in amniotic fluid from women who underwent amniocentesis and subsequently delivered healthy infants.…”