Second to fourth digit ratio: a predictor of adult testicular volume

Abstract

SUMMARYIt has been suggested that second to fourth digit ratio (digit ratio) may correlate with male reproductive system function or disorders. This hypothesis is based on finding that the Hox genes control finger development and differentiation of the genital bud during embryogenesis. Thus, we investigated the association between digit ratio and adult testicular volume. A total of 172 Korean men (aged 20-69 years) hospitalized for urological surgery were prospectively enrolled. Patients with conditions known to strongly influence testicular volume were excluded. Before determining testicular volume, the lengths of the second and fourth digits of the right hand were measured by a single investigator using a digital vernier calliper. Using orchidometry, the testes were measured by an experienced urologist who had no information about the patient's digit ratio. To identify the independent predictive factors influencing testicular volume, univariate and multivariate analyses were performed using linear regression models. Age, height, serum testosterone and free testosterone level were not correlated with testicular volume. Digit ratio, along with weight, was significantly correlated with testicular volume (right testicular volume: r = À0.185, p = 0.015; left testicular volume: r = À0.193, p = 0.011; total testicular volume: r = À0.198, p = 0.009). Multivariate analysis using linear regression models showed that only digit ratio was the independent factor to predict all (right, left and total) testicular volumes (right testicular volume: b = À0.174, p = 0.023; left testicular volume: b = À0.181, p = 0.017; total testicular volume: b = À0.185, p = 0.014). Our findings demonstrated that digit ratio is negatively associated with adult testicular volume. This means that men with a higher digit ratio may be more likely to have smaller testis compared to those with a lower digit ratio.

The relationship between the second‐to‐fourth digit ratios and lifelong premature ejaculation: a prospective, comparative study

“…This finding was similar to the previous studies about the relationship between digit ratio and adult sex hormone levels Bang et al, 2005;Muller et al, 2011;Oh et al, 2014). This finding was similar to the previous studies about the relationship between digit ratio and adult sex hormone levels Bang et al, 2005;Muller et al, 2011;Oh et al, 2014).…”

“…Sex differences in digit ratios develop early in childhood and are unaffected by pubertal growth (McIntyre, 2006). In another study, Oh et al (2014) reported that men with a higher digit ratio may be more likely to have smaller testis volumes compared to those with a lower digit ratio. These developments led to the use of 2D : 4D as a tool of investigating possible associations between prenatal sex hormone exposure and various behaviors, diseases, and disorders.…”

“…Recently, Choi et al (2011) investigated the relationship between 2D : 4D and penile length, and demonstrated that the patients with higher 2D : 4D had greater penile length. In another study, Oh et al (2014) reported that men with higher digit ratio may be more likely to have smaller testis compared to those with a lower digit ratio. Nevertheless, the effect of fetal androgens on ejaculatory process is not known.…”

The complexity of mating decisions in stalk‐eyed flies

“…Indirect evaluation mechanisms are plausible. Under normal conditions, females could have used the male ornament and body size, which are positively correlated with internal reproductive organ size (Cotton et al., ; Rogers et al., ), as is the case in several other insect species (Bangham et al., ; Fairn, Schulte‐Hostedde, & Yves, ; Oh, Kim, Yoon, Kim, & Kim, ). But in our experimental design any information from male eyespan was explicitly constrained so that it could not serve as a proxy for male reproductive organ size (these traits were not correlated, Pearson ρ 183 = −0.031, p = .682).…”

Can second to fourth finger ratio play a role in determining the risk of benign prostatic enlargement

“…And in our previous study, we found that anogenital distance, another indicator of prenatal androgenic exposure, was associated with the risk of prostate cancer (Sahin et al, ). Another study found that those with a higher 2D:4D finger ratio had lower testicular volumes than those with a lower 2D:4D finger ratio (Oh, Kim, Yoon, Kim, & Kim, ). In addition, there are studies suggesting that the finger ratio can predict adult penile size and that the effects of prenatal testosterone may partly explain the difference in adult penile size (Choi et al, ).…”