The study was a large case–control study with data collected over a period of 15 years, with similar rates of cases and controls recruitment. The subjects were asked to self-identify their pattern of index (2D) as compared to ring finger (4D). The results showed a negative association between length of 2D greater than 4D and prostate cancer risk (OR 0.67, 95% CI 0.57–0.80) in all ages and at ages <60 (OR 0.13, 95% CI 0.09–0.21) (results not shown). These negative associations suspect that lower prenatal activity of testosterone is protective against prostate cancer later in life.
The only study to investigate the relationship between digit length pattern and prostate cancer is the Korean Cohort study (366 subjects), which found a significant negative association between digit ratio and PSA (r
=0.007) (Jung et al, 2010
). Those with lower digit ratio had higher mean PSA level and higher risk of prostate biopsy (OR 1.75, 95% CI 1.07–2.84) and prostate cancer (OR 3.22, 95% CI 1.33–7.78).
Pictures of the right hand were provided to aid the response as there is a greater sex difference in 2D
4D on the right hand than on the left hand (Williams et al, 2000
). The procedure was particularly successful in terms of response rate (99% of eligible subjects responded to the question).
It has been suggested that intrauterine exposure of hormones influences the development of other adult-onset diseases (Manning and Bundred, 2000
), including a large study on finger pattern and osteoarthritis risk, in which lower digit ratio was associated with osteoarthritis (Zhang et al, 2008
). In the latter study, digit lengths were physically measured on hand radiographs using vernier callipers to achieve a high degree of accuracy and repeatability. This was considered impractical and unethical for our study; hence, hand radiographs were not used. Instead, we used a simpler way to identify the pattern of 2nd and 4th finger by self-reported comparison of the hand with pictures. The self-reported finger length, however, raises the possibility of measurement error, as discussed by Caswell and Manning. In their study, they used two different approaches to measure 2D
4D, including finger length measured from photocopies of the ventral surface of hands (photo 2D
4D) and self-reported finger length measured directly from the finger (S–R 2D
4D). The results suggested that self-reported 2D
4D showed some more extreme values when compared with photo 2D
4D. It was concluded, however, that a large sample size would reduce the effect size of this (Caswell and Manning, 2009
); hence, this possible error is unlikely to have a large effect in our study.
The finger length relationship seen in our study is also in keeping with equivalent studies in breast cancer risk based on current understanding of the role of hormonal patterns in utero
. Women with a high ratio of 2D
4D (indicative of higher prenatal oestrogen exposure) are at greater risk of breast cancer. Women with the more ‘feminine' pattern of digit length (2D
4D high – ring finger closer in length or shorter than the index finger) were also more likely to present at a younger age (Manning and Bundred, 2000
Although finger length in humans has been studied for decades, its relationship with hormones has been determined only by one relatively small-scale study (Lutchmaya et al, 2004
). In humans, the growth and pattern of digits and the differentiation of gonads is controlled by the homeobox genes HOXA
. Therefore, gonadal foetal products such as testosterone may influence finger morphology (Manning et al, 2003
). For example, a high concentration of testosterone, indicating high prenatal testicular activity leads to low 2D
4D ratio. The negative correlation between digit ratio and hormone profile has been used as a marker to predict offspring sex ratio and sporting ability (Robinson and Manning, 2000
; Williams et al, 2000
; Manning and Taylor, 2001
; Manning et al, 2002
). The ratio (2D
4D) is greater in the right hand than in the left hand, and has a higher sensitivity with foetal androgens than the left hand (Williams et al, 2000
). A high 2D
4D ratio in male right hands was associated with germ cell failure due to azoospermia or oligospermia with no motility; furthermore, testosterone assays from 58 male subjects were negatively associated with 2D
4D ratio in the right hand (P
=0.03), which was not seen in the left hand (Manning et al, 2000
). Twin studies suggest that there is also a possible genetic role in addition to any prenatal environmental influence on this hormonally related skeletal ratio in both men and women (Paul et al, 2006
; Gobrogge et al, 2008
A protective effect of a high 2D
4D hand pattern on prostate cancer risk was observed. High 2D
4D hand pattern may be the marker of low prenatal androgenic activity, suggesting the importance of hormone modulation in utero
on prostate cancer risk. Hand pattern might represent a simple marker for prostate cancer risk, particularly in men age under 60 years.